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ckermit2.txt：源码内容

indicated number of NUL bytes. If /SIZE was not given, this switch is
ignored.
/RPAD[:value]
Like LPAD, but pads on the right.
/CHARACTER
Specifies that one character should be written. If the <text> is empty or
not given, a NUL character is written; otherwise the first character of
<text> is given. Synonym: /BYTE.
/STRING
Specifies that the <text> is to be written as-is, with no terminator added.
Here's an example in which we copy a text file line by line:
file open /read %c oofa.txt ; Open input file
if fail exit 1 Can't open input file ; Check that it's open
file open /write %d new.txt ; Open output file
if fail exit 1 Can't open output file ; Check
while true { ; Loop to copy lines
file read /line %c line ; Read a line
if fail break ; Assume failure = end of file
file write /line %d {m(line)} ; Write the line to output file
if fail exit 1 Write failure ; Failure here is fatal
}
file close %c ; Close the two files
file close %d
Note that since /LINE is the default for both FILE READ and FILE WRITE, it can
be omitted as in the following example, where we also use the short names for
the FILE commands.
fopen /read %c oofa.txt ; Open input file
if fail exit 1 Can't open input file ; Check that it's open
fopen /write %d new.txt ; Open output file
if fail exit 1 Can't open output file ; Check
while true { ; Loop to copy lines
fread %c line ; Read a line
if fail break ; Assume failure = end of file
fwrite %d {m(line)} ; Write the line to output file
if fail exit 1 Write failure ; Failure here is fatal
}
fclose %c ; Close the two files
fclose %d
Here's the same example using "record i/o" (the open and close sequences are
are omitted since they are the same as above). The result is the same, but
execution is much faster:
while true { ; Loop to copy blocks
fread /size:512 %c block ; Read a block into %a
if fail break ; Assume failure = end of file
fwrite /string %d {m(block)} ; Write the block to output file
if fail exit 1 Write failure ; Failure here is fatal
}
Although record i/o is faster, it should not be used in line-oriented
applications, since it returns arbitrary chunks of the file to your script,
rather than lines. In this example, FWRITE /STRING is used rather than FWRITE
/SIZE:512 to avoid the last output block being padded beyond the original
file's length.
A file can also be copied character by character, but this is much slower than
line i/o and VERY much slower than block i/o:
while true { ; Loop to copy blocks
fread /char %c c ; Read a character into c
if fail break ; Assume failure = end of file
fwrite /char %d {m(c)} ; Write character to output file
if fail exit 1 Write failure ; Failure is fatal
}
Although character i/o is slow, it is the only way to process files that
contain NUL characters (i.e. bytes composed of only zero bits). In the
example above, when "fread /char %c c" returns a NUL, the c variable is
empty. But since the FREAD /CHAR command did not fail, we know the result was
really a NUL. FWRITE /CHAR, when given an empty variable (or no variable at
all) writes a NUL. Thus the loop above will copy any file at all (very
slowly). In non-copying applications, NULs are detected like this:
fread /char %c c
if fail (do something)
if not def c (a NUL byte was read)
Finally some advanced file operations:
FILE FLUSH <channel>
For output files only: commits all previous writes to disk,
in case the computer was buffering them. Synonym: FFLUSH.
FILE COUNT [ { /BYTES, /LINES, /LIST, /NOLIST } ] <channel>
By default, or if the /BYTES switch is given, counts the bytes in the
file, if any, open on the given channel. If the /LINES switch is given,
counts lines in the file. If the /LIST switch is given, the result is
printed. If the /NOLIST switch is given, the result is not printed.
/QUIET is a synonym for /NOLIST. If neither /LIST nor /NOLIST is given,
the result is printed if the command is given at top level, i.e. not from
a command file or macro. In all cases, the result of the most recent FILE
COUNT command is stored in the variable v(f_count). Note that FILE COUNT
/LINE works (and can only work) by reading the entire file; expect it to
take some time if the file is large. Synonym: FCOUNT.
FILE REWIND <channel>
Moves the read/write pointer to the beginning of the file. Equivalent to
FILE SEEK <channel> 0. Synonym: FREWIND.
FILE SEEK [ switches ] <channel> { [{+,-}]<number>, LAST, EOF }
Moves the read/write pointer for the file on this channel to the given
position, which may be a byte (character) number or a line number,
expressed in either absolute or relative terms. Switches:
/BYTE - The number given is a byte number. Synonym: /CHARACTER.
/LINE - The number given is a line number.
/ABSOLUTE - The number given is absolute.
/RELATIVE - The number given is relative to the current position.
By default, or if the /BYTE switch is given, the <number> is a
byte number (0 = first byte). If /LINE is given, the <number> is a line
number (0 = first line). EOF means to move to the end of the file.
LAST means to move to the last line or character of the file, depending
on whether it's a line or character seek.
If neither the /RELATIVE nor the /ABSOLUTE switch is given, then if a
signed number is given, the motion is relative to the current position.
An expression that evaluates to a negative number is not considered signed
for this purpose; that is, a sign (+ or -) must be included as the first
character of the <number> in the command itself to force a relative seek
(in the absence of /RELATIVE or /ABSOLUTE).
If the number has no sign, or if the /ABSOLUTE switch is given, the number
represents an absolute position (relative to the beginning of the file).
Subsequent FILE READs or WRITEs will take place at the new position.
If the read/write pointer is placed after the end of the file, a
subsequent FILE READ will fail, but a FILE WRITE will succeed (possibly
creating a file with "holes"). If a FILE SEEK /BYTE command is given, the
current line becomes unknown (unless the position is 0) and subsequent
FILE SEEK /RELATIVE /LINE commands will fail until the next non-relative
FILE SEEK /LINE command is given. Synonym: FSEEK.
An absolute FILE SEEK to a negative position fails silently, as does a
relative seek to a position before the beginning of the file.
A caution about relative SEEKs: remember that the number is relative to the
current position. Whenever you read or write, this changes the position.
In each of the following examples, assume the file open on channel %c is
positioned at line "n" (the FREAD target variable is omitted for lack of
space):
{ FREAD %c, FSEEK /LINE %c -1, FREAD %c } <-- Reads line n twice
{ FREAD %c, FSEEK /LINE %c +0, FREAD %c } <-- Reads lines n and n+1
{ FREAD %c, FSEEK /LINE %c +1, FREAD %c } <-- Reads lines n and n+2
{ FREAD %c, FSEEK /LINE %c -2, FREAD %c } <-- Reads lines n and n-1
{ FREAD %c, FSEEK /LINE %c -3, FREAD %c } <-- Reads lines n and n-2
Another caution: Using FSEEK and FREAD /SIZE to repeatedly read the same disk
block (e.g. when sampling a database record that is frequently updated) might
not give you updated disk blocks due to the internal buffering and caching of
the C library (this probably varies from one platform/compiler combination to
another). If necessary you can force a fresh disk read with a close/open
sequence:
FCLOS %c
FOPEN %c <samefilename>
FSEEK %c <samespot>
FREAD /SIZE:<howmanybytes> %c <variable>
1.22.3. FILE Command Examples
To read the last 10 lines of a text file into an array:
fopen /read %c oofa.txt ; Open the file
if fail exit 1 Can't open oofa.txt ; Always check for failure
dcl &a[10] ; Declare a 10-element array
fcount /line %c ; Count lines in the file
fseek /line %c v(f_count)-10 ; Seek to 10 lines from the end
if fail exit 1 Can't seek ; Check for failure
for %i 1 10 1 { fread %c &a[%i] } ; Read the last 10 lines
fclose %c ; Close the file
Note that blank lines show up as empty (undefined) array elements, for example
if you give a "show array a" command at this point. This is normal. You
can still use these elements; e.g.:
for %i 1 10 1 { echo %i. &a[%i] } ; Display the 10 lines
Here is how to read the last line of a file (already open on channel %c):
fseek /line %c last ; Seek directly to last line
Alternatively:
fseek /line %c eof ; Seek to end of file
fseek /line %c -1 ; Seek to beginning of last line
Alternatively:
fcount /line %c ; Count the file's lines
fseek /line %c v(f_count)-1 ; Seek to last line
fread %c ; Read it
To read every other line from the file (using relative SEEK), skipping
the first line:
fopen /read %c oofa.txt ; Open the file
while ( success ) { ; Loop through lines
fseek /line %c +1 ; Skip a line
if success fread %c ; Read & display a line
}
fclose %c ; Close the file
Here is how to read the lines of a file in reverse order:
fopen /read %c oofa.txt ; Open
if fail exit 1 ; Check
fseek /line %c last ; Seek to last line
while success { ; Loop
fread %c ; Read line
fseek /line %c -2 ; Seek backwards two lines
}
fclose %c ; Close the file
The loop works because a relative SEEK outside the file fails.
It is also possible to use block i/o to manage random-access files with
fixed-length records (as long as they don't contain NUL characters). Suppose,
for example, you have a file of "card image" records with fixed-field
information about customers, such as:
Name: Columns 1-32 (column numbers are 1-based)
Address: Columns 33-72
Balance: Columns 73-80
The records are indexed by customer number, starting with 0. There are no
line terminators separating them. Therefore the record for customer number
n starts at position n x 80 (%n*80).
Now suppose we received a payment from customer number 173 and want to update
the balance:
.%n = 173 ; Customer (record) number
.%a = 12.72 ; Amount
fopen /read /write %c customer.db ; Open the file
if fail stop 1 OPEN FAILED: f_errmsg() ; Check
fseek /byte %c 80*%n ; Seek to record
fread /size:80 %c r ; Read the record
if fail stop 1 READ FAILED: f_errmsg() ; Check (IMPORTANT)
.%b := fright(m(r),8) ; Extract the balance
.%b := ffpadd(%b,%a,2) ; Add the new payment
if fail stop 1 ARITHMETIC ERROR: %b/%a ; Catch bad records
.r := {fleft(m(r),72)flpad(%b,8)} ; Update the record
fseek /byte %c 80*%n ; Reposition to same spot
fwrite /size:80 %c {m(r)} ; Replace the record
if fail stop 1 WRITE FAILED: f_errmsg() ; Check
fclose %c ; Close the file
REMEMBER: Using FILE SEEK to move beyond the end of file can result in a file
with holes when writing; when reading, an end-of-file error will occur --
be sure to check for it.
1.22.4. Channel Numbers
C-Kermit's channel numbers are integers from 0 to some platform-dependent
limit, such as 46 or 1985 (the value of v(f_max)). This is the limit placed
by the operating system on the number of files that may be opened by one
process or user or job, minus the standard input, output, and error files, and
minus the number of files reserved by C-Kermit for logs, OPEN READ and WRITE,
and file transfer (and maybe some command files -- the v(f_max) number can't
be exact).
Although you must include a variable in the FILE OPEN command, to which the
channel number is assigned, you don't have to use a variable in the other FILE
commands if you know what the number is -- you can just put the number. This
saves you a few keystrokes when typing commands at the prompt:
fopen %c oofa.txt
flist
0. /usr/olga.oofa.txt (R) 0
This tells the channel number is 0 (the number on the left is the channel
file's channel number). Of course you can also find it by echoing the
variable:
echo %c
0
Or with "fstatus %c". Now you can type commands like:
fread 0
to read a line from the file. Obviously, however, using digits rather than
a variable for the channel number would be poor practice in a script.
If in commands like:
fread %c %a
you have trouble remembering which variable is which, note that the channel
number is, indeed, a number. Anywhere C-Kermit accepts a number it can also
accept an expression, so you can put parentheses around the channel number to
remind you it's the channel number and not the variable into which data is to
be read:
fread (%c) %a
Normally channel numbers are assigned sequentially as 0, 1, 2, ... up to the
limit. However, once you start closing files, there can be holes in the
sequence. New channels are assigned to fill in the holes. Thus you can't
depend on channel numbers being in any particular sequence.
1.22.5. FILE Command Errors
Each FILE command sets the variable v(f_error) to one of the following values:
0 = No error
-1 = System error
-2 = Attempt to read after end of file
-3 = Channel not open
-4 = Channel number out of range (negative or too large)
-5 = Numeric argument (size, ...) out of range
-6 = File not found
-7 = Bad or missing filename
-8 = Too many files are already open (FILE OPEN only)
-9 = Forbidden operation (e.g. write to a read-only file)
-10 = Access denied
-11 = Illegal combination of OPEN modes (FILE OPEN only)
-12 = Buffer overflow
-13 = Current line number unknown (for relative line seeks)
-14 through -98: Reserved.
-99 = Requested operation not implemented in this version of C-Kermit
-999 = Unknown error
When v(f_error) is -1, this means the FILE command failed because because
of a system error, in which case you can examine the following variables:
v(errno) = System error number.
v(errstring) = Error message corresponding to v(errno).
A special function is available for translating the v(f_error) code to an
error message string:
f_errmsg([code])
If the code is -1, returns error message of the most recent system
error; otherwise if the code is a valid v(f_error) value, the associated
message is returned. If the code is omitted, the status message
corresponding to the current v(f_error) value is returned.
A FILE command that fails prints the appropriate error message automatically,
except when the command is READ or SEEK and the error is -2 (end of file); in
that case, the command still fails, but does not print a message. This allows
constructions such as:
fopen %c oofa.txt
while success { fread %c }
fclose %c
to work as expected, i.e. without an annoying message when the end of file
is reached.
1.22.6. File I/O Variables
The variables associated with the file i/o package are:
v(f_count) - Result of the most recent FILE COUNT (FCOUNT) command.
v(f_error) - Numeric error code of most recent FILE command (0 = no error).
v(f_max) - Maximum number of files open simultaneously.
1.22.7. File I/O Functions
Some of the FILE commands can also be issued as function calls, which makes
script writing a bit more convenient, especially for C programmers. Also,
several functions are provided that do not have command equivalents. Each of
these functions takes a channel number as the first argument. These functions
do not work for OPEN { READ, !READ, WRITE, !WRITE, and APPEND } files.
f_status(channel)
Returns 0 if the channel is not open, otherwise a number between 1 and 15
which is the sum of the OPEN modes:
1 = /READ
2 = /WRITE
4 = /APPEND
8 = /BINARY
The remaining functions work only for open channels. Each of these functions
can fail for the applicable reasons listed in Section 1.22.5. For instructions
on handling function errors, see Section 7.12.
f_pos(channel)
Returns the file's current read/write pointer (0-based). There is no FILE
command equivalent.
f_line(channel)
Returns the file's current line number (0-based), if known, otherwise -1.
There is no FILE command equivalent. The line number is known as long as
no character or block i/o has been done on the channel.
f_handle(channel)
Returns the "file handle" of the file. That is, it translates the portable
C-Kermit channel number into a system-specific file handle or number that
can be passed to other programs on the same platform. In UNIX this is a
file descriptor. There is no FILE command equivalent.
f_eof(channel)
Returns 1 if the read/write pointer of the file on the given channel is at
the end of the file, 0 otherwise. Convenient in WHILE statements, e.g.:
while not f_eof(%c) { fread %c }
f_getchar(channel)
Equivalent to FREAD /CHAR. Returns the character actually read.
If f_getchar() does not fail but the return value is empty, this means
a NULL character was read.
f_getline(channel)
Equivalent to FREAD /LINE. Returns the line actually read, but with the line
terminator stripped. If f_getline() does not fail but the return value is
empty, this normally means an empty line was read.
f_getblock(channel,n)
Equivalent to FREAD /SIZE:n. Returns the block of characters actually read.
If the returned block is smaller than n, it indicates either that the end
of file was reached or a NUL character is in the block.
f_putchar(channel,c)
Equivalent to FWRITE /CHARACTER. Writes the character c. If c contains
more than one character, only the first is written. If c is empty a NUL
is written. Returns the number of characters written on success, or a
negative error code upon failure.
f_putline(channel,string)
Equivalent to FWRITE /LINE. Writes the string and adds the appropriate line
termination character or sequence. If the string is empty or omitted, an
empty line is written. Returns the number of characters written on success,
or a negative error code upon failure.
f_putblock(channel,string)
Equivalent to FWRITE /STRING. Writes the string as given. If the string is
empty or omitted, nothing is written. Returns the number of characters
written on success, or a negative error code upon failure.
1.22.8. File I/O Function Examples
fopen /read %c oofa.txt ; Open our favorite file for reading
if failure exit 1 ; Check that it's open
while not f_eof(%c) { ; Loop until EOF
.line := f_getline(%c) ; Get a line
if success echo {m(line)} ; Echo it
}
if not f_eof(%c) { ; Check reason for loop exit
exit 1 File Error: f_errmsg() ; If not EOF say so.
}
frewind %c ; Rewind the file
while not f_eof(%c) { ; Same thing but with block i/o
.block := f_getblock(%c,256) ; (much faster than line i/o)
if success xecho {m(block)}
}
frewind %c ; Rewind again
while not f_eof(%c) { ; Same deal but with character i/o
.c := f_getchar(%c) ; (much slower than line i/o)
if success xecho {m(c)}
}
close %c
To close all open files (equivalent to FCLOSE ALL):
for %i 0 v(f_max)-1 1 {
if f_status(%i) fclose %i
}
1.23. The EXEC Command
The EXEC command is available only in UNIX.
EXEC [ /REDIRECT ] <command> [ <arg1> [ <arg2> [ ... ] ]
Runs the given command with the arguments in such a way that the <command>
replaces C-Kermit in memory, and C-Kermit ceases to execute. EXEC is like
RUN, except instead of returning to C-Kermit when finished, the <command>
returns to whatever process invoked Kermit.
In the normal case, no files are closed, so the EXEC'd command inherits the
open files, read/write pointers, working directory, process ID, user ID
(unless <command> is SUID), group ID (unless command is SGID), groups, etc.
(In UNIX, the EXEC command is simply a front end for execvp().)
If the /REDIRECT switch is included, then if a connection is open (SET LINE
or SET HOST), it becomes the standard input and output of the EXEC'd program.
If no connection is open, the /REDIRECT switch has no effect. For example
to use C-Kermit for PPP dialing in Linux:
set modem type usr ; Specify the kind of modem you have
set line /dev/ttyS1 ; Specify the device it's connected to
set speed 57600 ; and the speed
set flow rts/cts ; and flow control.
set dial retries 100 ; Try the dial sequence up to 100 times.
dial {{9-212-555-1212}{9-212-555-1213}{9-212-555-1214}{9-212-555-1215}}
if fail exit 1
for %i 1 16 1 { ; Try up to 16 times to get login prompt
input 10 Login: ; Wait 10 sec for it to appear
if success break ; Got it - proceed...
output 13 ; Send a carriage return and try again
}
if ( > %i 16 ) stop 1 NO LOGIN PROMPT
lineout (myuserid) ; Send user ID
input 30 assword: ; Wait for Password prompt
if fail stop 1 NO PASSWORD PROMPT
lineout m(mypassword) ; Send the password.
exec /redirect pppd ; Replace ourselves with pppd.
In this example we assume that the script has already set up the myuserid and
mypassword variables -- normally the password should be prompted for, rather
than stored on disk. Notice the advantages over the well-known "chat script":
. You don't have to control the modem itself with AT commands; Kermit's
DIAL command does this for you.
. You can have Kermit automatically redial as many times as you want
until it gets a connection (if this is legal in your country).
. You can have Kermit fetch the number or numbers from a dialing directory.
. You can have Kermit cycle through a list of phone numbers (this is new
to C-Kermit 7.0; see Section 2.1.16) without having to enter the numbers
in a dialing directory.
. Dialing is location-independent; you can use the same script to dial from
different areas or countries.
. Once the connection is made, the full power of Kermit's script language
is available to manage the dialog with the terminal server or other
device that answers the phone call.
1.24. Getting Keyword Lists with '?'
Suppose you type "te" at the C-Kermit> prompt and then Esc or Tab to request
keyword completion. Kermit beeps, indicating that more than one command
starts with "te". But if you type '?' to see what they are, Kermit shows
only "telnet". So why the beep? Because of invisible keywords like "telopt",
"terminal", and "text". Lots of keywords are invisible because they are
either synonyms for other keywords or else esoteric options to be used only
in special circumstances, so we don't want them cluttering up the menus.
But then there is no way for you to discover them. So in C-Kermit 7.0, if you
type '?' AFTER the beginning of a keyword field, then invisible keywords are
shown too:
C-Kermit>te<Esc><BEEP>
C-Kermit>te? Command, one of the following:
telnet telopt terminal text
C-Kermit>te
But if '?' is typed at the beginning of a field, only visible keywords are
shown, as before (so, in this example, if '?' is typed at the C-Kermit>
prompt, "telnet" is the only command shown that starts with "te").
(2) MAKING AND USING CONNECTIONS
The SET LINE, SET HOST, and SET PORT (a synonym for SET LINE) commands have
new synonyms, in which the word SET is replaced by the word OPEN: OPEN LINE,
etc. There is no new functionality here, but OPEN is a better verb, since SET
generally takes no action, whereas these commands actually try to open a
connection. Furthermore, there is the symmetry with CLOSE.
2.0. SET LINE and SET HOST Command Switches
The SET LINE (SET PORT) and SET HOST commands now allow switches before the
device or host name, in most cases, and under certain circumstances, also at
the end. The new syntax is backwards compatible with the previous syntax;
thus SET LINE, SET PORT, and SET HOST commands in command files written for
C-Kermit 6.0 or earlier still work. The expanded syntax is:
{ OPEN,SET } { LINE,PORT,HOST } [ switches ] <device-or-address> [ switches ]
The first group of switches is:
/NETWORK-TYPE:{TCP/IP,X.25,PIPE,PTY...}
When more than one network type is available, this lets you specify the
type of network to use for this connection without affecting your global
SET NETWORK TYPE. See Section 2.7 about pipes and ptys.
/USERID:[string]
This switch is equivalent to SET LOGIN USERID. If a string is given, it
sent to host during Telnet negotiations; if this switch is given but the
string is omitted, no user ID is sent to the host. If this switch is not
given, your current LOGIN USERID (v(userid) value), if any, is sent.
Unlike most other switches, this one is "sticky", since the value must
persist throughout the session in case the server requests the ID string
at a later time.
/CONNECT
Enter CONNECT mode immediately and automatically after the device or
connection is open. On serial devices, however, when CARRIER-WATCH is
not OFF, wait up to 1 second for the Carrier Detect signal to appear
before trying to connect, to give the device time to react DTR, which
might have been off prior to opening the device.
/SERVER
Enter server mode immediately and automatically after the device or
connection is open. Treatment of carrier is the same as for /CONNECT.
/WAIT
/NOWAIT
For Telnet connections only: Like SET TELNET WAIT { ON, OFF }, but applies
only to this connection, and in fact applies only when OPENing this
connection (which is usually the only place it matters). Typically you
would use TELNET /NOWAIT to make a connection to a misbehaving Telnet
server that does not reply to negotiations as required by the Telnet
protocol definition.
Note: /CONNECT and /SERVER switches are not available in the RLOGIN and TELNET
commands, since these commands already include an implicit /CONNECT and
preclude automatic entry into server mode.
The /CONNECT and /SERVER switches are especially useful with "set host *"
connections. For example, suppose you want to start a Kermit server on socket
3000 of your TCP host. Normally you would have to give the command:
set host * 3000
and then wait for a connection to come in, and only then could you give the
SERVER command (or else define a macro to do this, and then execute the macro).
Now you can do it in one step:
set host /server * 3000
This tells C-Kermit to wait for the connection and then enter server mode
once it comes in, no matter how long it takes. Similarly, "set host /conn *"
can be used to wait for a "chat" connection to come in.
Another set of switches is available in VMS only, for use only with SET LINE:
/SHARE
Allows the SET LINE device to be opened in shared mode. Normally it makes
no sense to open a serial device in shared mode, but it's necessary when
C-Kermit is running in an environment such as DECIntact, that opens your
job's controlling terminal in such a way that C-Kermit can't open it too,
unless it enables SHARE privilege. Note: SHARE privilege is required.
/NOSHARE
Requires that the SET LINE device not be in use by any other process in
order for it to be successfully opened by C-Kermit. If neither /SHARE nor
/NOSHARE is specified, /NOSHARE is used.
The second group of switches is:
/NO-TELNET-INIT
Do not send initial Telnet negotiations even if this is a Telnet port.
/RAW-SOCKET
This is a connection to a raw TCP socket (Section 2.3.5).
/RLOGIN
Use Rlogin protocol even if this is not an Rlogin port.
/TELNET
Send initial Telnet negotiations even if this is not a Telnet port.
As of C-Kermit 7.0 and K95 1.1.18, the TELNET command includes an implicit
/TELNET switch. So if you TELNET to a non-TELNET port, Kermit sends initial
Telnet negotiations. This makes sense, since that's what "telnet" means.
If you want to make a connection to a non-Telnet port without sending initial
Telnet negotiations, use:
set host [ /connect ] <name-or-address> <port>
or:
telnet <name-or-address> <port> /no-telnet-init
Additional switches might be added in the future; type "set host ?" or "set
line ?" to see a current list.
2.1. Dialing
Automatic redialing is illegal or restricted in many countries, so until
C-Kermit 7.0, it was disabled by default, i.e. until a SET DIAL RETRIES
command was given. In C-Kermit 7.0, if no SET DIAL RETRIES command has been
given, a default is picked dynamically at DIAL time based on the calling
country code, if known. At this writing, the only country code known to have
no restrictions on automatic redialing is 1. So in this case a limit of 10
is chosen; otherwise 1. If you have not given an explicit SET DIAL RETRIES
command, SHOW DIAL shows the value as "(auto)", and then the value actually
used is shown when you give the DIAL command.
As of C-Kermit 7.0, automatic redialing is automatically canceled if the
call could not be placed because no dialtone was detected.
2.1.1. The Dial Result Message
If DIAL DISPLAY is not ON, the "Call complete" message now shows the modem's
call result message, for example:
Dialing: ...
Call complete: "CONNECT 31200/ARQ/V32/LAPM/V42BIS"
The exact format and contents of this message, of course, depends on the
make, model, and configuration of your modem, so use your modem manual to
interpret it. The call result message is also available in C-Kermit's
v(dialresult) variable.
C-Kermit> echo v(dialresult)
CONNECT 31200/ARQ/V32/LAPM/V42BIS
C-Kermit> echo Speed = fword(v(dialresult),2)
Speed = 31200
C-Kermit>
Suppose your modem reports the modulation speed as shown above and you want to
ensure your call is completed at (say) 24000 bps or more. You can use a
little macro to do the job:
define HSDIAL { ; High Speed DIAL
local %s
if < v(argc) 1 if not def v(dialnumber) end 1 Usage: %0 number
set dial retries 100
set dial interval 1
while true {
dial %*
if fail end 1 DIAL failed.
asg %s fword(v(dialresult),2)
if def %s if numeric %s if not < %s 24000 break
}
}
(See section 7.5 about the %* variable.)
2.1.2. Long-Distance Dialing Changes
Due to the glut of cell phones, pagers, fax machines, ISPs, etc, area codes
and dialing rules are changing all the time. In the North American Numbering
Plan (NANP) countries (USA, Canada, etc), area codes are split or overlayed
with increasing frequency, and 10- and 11-digit dialing is gradually becoming
the norm for local calls. Changes are occurring In Europe, too, partly for
these reasons and partly because of some new EC rules.
In France, effective 18 October 1996, all calls, even local ones, must be
dialed with an area code. French area codes are presently 1-digit numbers,
1-6, and the long-distance dialing prefix is 0. All calls within France are
considered long distance and begin with 01, 02, ..., 06.
Effective 1 May 1997, all calls within the US state of Maryland, even local
ones, must be dialed with an area code but WITHOUT the long-distance prefix --
this is the now widely-known North American phenomenon of "ten digit dialing".
The same is happening elsewhere -- many cities in Florida adopted 10-digit
dialing in 1998.
In Italy beginning 19 June 1998, all calls to fixed (as opposed to mobile)
numbers must be prefixed by 0. When calling into Italy from outside, the 0
must follow the country code (39). Calls to cell phones, however, must be
placed without the 0. Then on 29 December 2000, the 0 will become a 4 (for
calling fixed numbers) and a prefix of 3 must used for calling mobile phones.
More info at: http://www.telecomitalia.it/npnn/.
In Spain, effective 4 April 1998, with hard cutover on 18 July 1998, all
calls within the country must be dialed with 9 digits, and all calls from
outside Spain must also be dialed with 9 digits (after the country code, 34).
The new 9-digit numbers all begin with "9". More info at:
http://www.telefonica.es/cambiodenumeracion/
Several new dialing features and commands have been added in version 6.1 and
7.0 to address these changes.
C-Kermit 6.0 and Kermit 95 1.1.11 and earlier handle the French situation
via a reasonable subterfuge (setting the local area code to a nonexistent
one), but did not handle "ten-digit dialing" well at all; the recommended
technique was to change the long-distance dialing prefix to nothing, but this
defeated Kermit's "list numbers for one name" feature when the numbers were in
different locations. For example:
set dial ld-prefix
dial onlineservice
where "onlineservice" is a dialing directory entry name corresponding to
entries that are in (say) Maryland as well as other states, would not
correctly dial the numbers not in Maryland.
A new command lets you specify a list of area codes to be considered local,
except that the area code must be dialed:
SET DIAL LC-AREA-CODES [ areacode [ areacode [ areacode [ ... ] ] ] ]
The list may include up to 32 area codes. If a number is called whose area
code is in this list, it is dialed WITHOUT the long-distance prefix, but WITH
the area code. So in Maryland, which (last time we looked) has two area
codes, 410 and 301, the setup would be:
SET DIAL LC-AREA-CODES 410 301
Example:
SET DIAL LD-PREFIX 1
SET DIAL AREA-CODE 301
SET DIAL LC-AREA-CODES 410 301 <-- Area codes in 10-digit dialing region
DIAL +1 (301) 765-4321 <-- Dials 3017654321 (local with area code)
DIAL +1 (410) 765-4321 <-- Dials 4107654321 (local with area code)
DIAL +1 (212) 765-4321 <-- Dials 12127654321 (long distance)
The SET DIAL LC-AREA-CODES command does not replace the SET DIAL AREA-CODE
command. The latter specifies the area code you are dialing from. If the
called number is in the same area code, then the area code is dialed if it is
also in the LC-AREA-CODES list, and it is not dialed otherwise. So if "301"
had not appeared in the LC-AREA-CODES list in the previous example:
SET DIAL LD-PREFIX 1
SET DIAL AREA-CODE 301
SET DIAL LC-AREA-CODES 410 <-- Area codes in 10-digit dialing region
DIAL +1 (301) 765-4321 <-- Dials 7654321 (local)
DIAL +1 (410) 765-4321 <-- Dials 4107654321 (local with area code)
DIAL +1 (212) 765-4321 <-- Dials 12127654321 (long distance)
The new Kermit versions also add a Local Call Prefix and Local Call Suffix, in
case you have any need for it. These are added to the beginning and of local
phone numbers (i.e. numbers that are not long-distance or international).
Examples:
SET DIAL LD-PREFIX 1
SET DIAL LC-PREFIX 9
SET DIAL LC-SUFFIX *
SET DIAL LC-AREA-CODES 410 <-- Area codes in 10-digit dialing region
SET DIAL AREA-CODE 301
DIAL +1 (301) 765-4321 <-- Dials 97654321* (local)
DIAL +1 (410) 765-4321 <-- Dials 94107654321* (local with area code)
DIAL +1 (212) 765-4321 <-- Dials 12127654321 (long distance)
2.1.3. Forcing Long-Distance Dialing
Suppose a number is in your country and area, but for some reason you need to
dial it long-distance anyway (as is always the case in France). There have
always been various ways to handle this:
1. Temporarily set your area code to a different (or nonexistent or
impossible) one (but this required knowledge of which area codes were
nonexistent or impossible in each country).
2. Dial the number literally instead of using the portable format, but this
defeats the purpose of the portable dialing directory.
Now there is also a new command that, very simply, can force long-distance
dialing:
SET DIAL FORCE-LONG-DISTANCE { ON, OFF }
If a call is placed to a portable phone number within the same country
code as the calling number, it is dialed with the long-distance prefix
and the area code if FORCE-LONG-DISTANCE is ON. If OFF, the regular
rules and procedures apply.
Example (France):
SET DIAL COUNTRY-CODE 33
SET DIAL AREA-CODE 6
SET DIAL FORCE-LONG-DISTANCE ON
(In fact, SET DIAL COUNTRY-CODE 33 automatically sets DIAL FORCE-LONG-DISTANCE
ON...)
Example (USA, for a certain type of reverse-charge calling in which the
called number must always be fully specified):
SET DIAL PREFIX 18002666328$ ; 1-800-COLLECT
SET DIAL COUNTRY-CODE 1
SET DIAL AREA-CODE 212
SET DIAL FORCE-LONG-DISTANCE ON
Example (Toronto, where calls to exchange 976 within area code 416 must be
dialed as long distance, even when you are dialing from area code 416):
SET DIAL COUNTRY-CODE 1
SET DIAL AREA-CODE 416
SET DIAL FORCE-LONG-DISTANCE ON
DIAL +1 (416) 976-xxxx
If dialing methods were consistent and sensible, of course it would be
possible to always dial every domestic call as if it were long distance. But
in many locations this doesn't work or if it does, it costs extra. The
following macro can be used for dialing any given number with forced
long-distance format:
define LDIAL {
local %x
set dial force-long-distance on
dial %*
asg %x v(success)
set dial force-long-distance off
end %x
}
(See section 7.5 about the %* variable.)
2.1.4. Exchange-Specific Dialing Decisions
This applies mainly to the North American Numbering Plan (NANP). Refer to the
section "Alternative notations" in "Using C-Kermit" 2nd Edition, pages
106-107, and the story about Toronto on page 110. Using the new LC-AREA-CODES
list, we can address the problem by treating the exchange as part of the area
code:
SET DIAL LD-PREFIX 1
SET DIAL AREA-CODE 416
SET DIAL LC-AREA-CODES 905276
DIAL +1 416 765 4321 <-- 7654321 (local)
DIAL +1 905 276 4321 <-- 9052764321 (local with area code)
DIAL +1 905 528 4321 <-- 19055284321 (long distance)
The same technique can be used in Massachusetts (story at top of page 111)
and in any other place where dialing to some exchanges within a particular
area code is local, but to others in the same area code is long distance.
2.1.5. Cautions about Cheapest-First Dialing
Kermit does not maintain a knowledge base of telephony information; it only
provides the tools to let you enter a phone number in a standard format and
dial it correctly from any location in most cases.
In particular, Kermit does not differentiate the charging method from the
dialing method. If a call that is DIALED as long-distance (e.g. from 212 to
718 in country code 1) is not CHARGED as long distance, we have no way of
knowing that without keeping a matrix of charging information for every
area-code combination within every country, and any such matrix would be
obsolete five minutes after it was constructed. Thus, "cheapest-first"
sorting is only as reliable as our assumption that the charging method follows
the dialing method. A good illustration would be certain online services that
have toll-free dialup numbers which they charge you a premium (in your online
service bill) for using.
2.1.6. Blind Dialing (Dialing with No Dialtone)
C-Kermit's init string for Hayes-like modems generally includes an X4 command
to enable as many result codes as possible, so that Kermit can react
appropriately to different failure reasons. One of the result codes that X4
enables is "NO DIALTONE". A perhaps not obvious side effect of enabling this
result code that the modem must hear dialtone before it will dial.
It is becoming increasingly necessary to force a modem to dial even though it
does not hear a dialtone on the phone line; for example, with PBXs that have
strange dialtones, or with phone systems in different countries, or with ISDN
phones, etc. This is called "blind dialing".
C-Kermit 7.0 has two new commands to cope with this situation:
SET DIAL IGNORE-DIALTONE { ON, OFF }
OFF (the default) means to tell the modem to wait for dialtone before
dialing. ON means to enable "blind dialing", i.e. tell the modem NOT
to wait for dialtone before dialing. Generally this is accomplished by
sending ATX3 to the modem just prior to dialing. SET MODEM TYPE xxx
and then SHOW MODEM displays Kermit's built-in "ignore dialtone" command.
SET DIAL COMMAND IGNORE-DIALTONE <text>
This lets you change the built-in ignore-dialtone command (such as ATX3)
to whatever you choose, in case the built-in one does not work, or another
command works better.
Notes:
1. The ignore-dialtone command is not sent unless SET DIAL IGNORE-DIALTONE
is ON.
2. The ATX3 command generally disables not only NO DIALTONE, but also BUSY.
So this will prevent Kermit from detecting when the line is busy. This
is a property of the modem, not of Kermit.
2.1.7. Trimming the Dialing Dialog
The command:
SET MODEM COMMAND <action> [ <command> ]
is used to override Kermit's built-in modem commands for each action, for
each kind of modem in its internal database. If you include a <command>,
this is used instead of the built-in one. If you omit the <command>, this
restores the original built-in command.
If you want to omit the command altogether, so Kermit doesn't send the command
at all, or wait for a response, use:
SET MODEM COMMAND <action> {}
That is, specify a pair of empty braces as the command, for example:
SET MODEM COMMAND ERROR-CORRECTION ON {}
2.1.8. Controlling the Dialing Speed
The rate at which characters are sent to the modem during dialing is normally
controlled by the built-in modem database. You might want to override this
if Kermit seems to be dialing too slowly, or it is sending characters to the
modem faster than the modem handle them. A new command was added for this
in C-Kermit 7.0:
SET DIAL PACING <number>
Specifies the number of milliseconds (thousandths of seconds) to pause
between each character when sending commands to the modem during DIAL or
ANSWER command execution. 0 means no pause at all, -1 (the default) or any
other negative number means to use the value from the database. Any number
greater than 0 is the number of milliseconds to pause.
HINT: You might also need to control the rate at which the modem generates
Touch Tones during dialing, for example when sending a numeric page. There
are two ways to do this. One way is to insert pause characters into the
dialing string. For modems that use the AT command set, the pause character
is comma (,) and causes a 2-second pause. On most modems, you can use the S8
register to change the pause interval caused by comma in the dialing string.
The other way is to set your modem's tone generation interval, if it has a
command for that. Most AT-command-set modems use S11 for this; the value is
in milliseconds. For example on USR modems:
ATS11=200
selects an interval of 200 milliseconds to separate each dialing tone.
Hint: To add S-Register settings or other commands to your dialing procedure,
use the new SET MODEM COMMAND PREDIAL-INIT command (Section 2.2.2).
2.1.9. Pretesting Phone Number Conversions
The LOOKUP command now accepts telephone numbers as well as directory-entry
names, for example:
LOOKUP +1 (212) 7654321
When given a phone number, LOOKUP prints the result of converting the phone
number for dialing under the current dialing rules. For example, if my
country code is 1 and my area code is 212, and I am dialing out from a PBX
whose outside-line prefix is "93,":
C-Kermit> lookup +1 (212) 7654321
+1 (212) 7654321 => 93,7654321
C-Kermit>
You can also use the fdialconvert(phone-number) function (Section 2.1.11)
to do this programmatically:
C-Kermit> echo "fdialconvert(+1 (212) 7654321)"
"93,7654321"
C-Kermit>
So the new LOOKUP behaves as follows:
LOOKUP <portable-format-phone-number>
Displays how the number would actually be dialed
Sets FAILURE if there was a conversion error, otherwise SUCCESS.
LOOKUP <literal-format-phone-number>
Displays the same <literal-format-phone-number>
Always sets SUCCESS.
LOOKUP <dialing-directory-name>
Displays all matching entries and converts portable phone numbers.
Sets SUCCESS if at least one entry was found, otherwise FAILURE.
LOOKUP =anything
Displays "=anything" and sets SUCCESS.
There is, at present, no programmatic way to fetch numbers from the dialing
directory. This will be considered for a future release.
2.1.10. Greater Control over Partial Dialing
The following rules now apply to partial dialing:
. Phone number transformations based on country and area code,
application of prefixes, etc, are performed only on the first PDIAL.
. Each PDIAL argument is looked up in the dialing directory, so it is
possible have directory entries for pieces of phone numbers or other
information.
. Suffixes are not applied automatically, since there is no way for C-Kermit
to know in which PDIAL segment you want them to be applied.
However, the suffix that *would* have been applied, based on the dialing rules
that were invoked when processing the first PDIAL command, is stored in the
variable:
v(dialsuffix)
which you can include in any subsequent PDIAL or DIAL commands.
Example:
pdial {m(my_long_distance_pager_number_part_1)}
pdial {m(my_long_distance_pager_number_part_2)}
pdial {v(dialsuffix)}
pdial {m(my_long_distance_pager_number_part_3)}
pdial {@m(numeric_pager_code)#}
2.1.11. New DIAL-related Variables and Functions
fdialconvert(s)
s is a phone number in either literal or portable format (not a dialing
directory entry name). The function returns the dial string that would
actually be used by the DIAL command when dialing from the current location,
after processing country code, area code, and other SET DIAL values, and
should be the same as the result of LOOKUP when given a telephone number.
v(dialsuffix)
Contains the suffix, if any, that was applied in the most recent DIAL
command, or the suffix that would have been applied in the most recent PDIAL
command. Use this variable to send the dial suffix at any desired point in
a PDIAL sequence.
v(dialtype)
A number indicating the type of call that was most recently placed. Can
be used after a normal DIAL command, or after the first PDIAL command in
a PDIAL sequence. Values are:
-2: Unknown because TAPI handled the phone number translation.
-1: Unknown because some kind of error occured.
0: Internal within PBX.
1: Toll-free.
2: Local within calling area.
3: Unknown (e.g. because a literal-format phone number was given).
4: Long distance within country.
5: International
v(dialcount)
The current value of the DIAL retry counter, for use in a DIAL macro
(Section 2.1.13).
v(d$px)
PBX Exchange (see Section 2.1.12).
Other dial-related variables, already documented in "Using C-Kermit" (or
other sections of this document, e.g. 2.1.1), include v(dialnumber),
v(dialstatus), etc. A convenient way to display all of them is:
show variable dial ; hint: abbreviate "sho var dial"
This shows the values of all the variables whose names start with "dial".
Also "show variable d$" (to show the v(d$...) variables).
2.1.12. Increased Flexibility of PBX Dialing
Refer to "Using C-Kermit", 2nd Edition, pages 107-108. Recall that three
commands are needed to configure C-Kermit for dialing from a PBX:
SET DIAL PBX-EXCHANGE <number>
SET DIAL PBX-INSIDE-PREFIX <number>
SET DIAL PBX-OUTSIDE-PREFIX <number>
Unfortunately, this model does not accommodate PBXs that have more than one
exchange. For example our PBX at Columbia University (which must handle more
than 10,000 phones) has 853-xxxx and 854-xxxx exchanges.
Beginning in C-Kermit 7.0, the SET DIAL PBX-EXCHANGE command accepts a list of
exchanges, e.g.:
SET DIAL PBX-EXCHANGE 853 854
(multiple exchanges are separated by spaces, not commas).
So now when dialing a portable-format number that has the same country and
area codes as those of your dialing location, C-Kermit compares the exchange
of the dialed number with each number in the PBX Exchange list (rather than
with a single PBX Exchange number, as it did formerly) to determine whether
this is an internal PBX number or an external call. If it is an external
call, then the PBX Outside Prefix is applied, and then the normal dialing
rules for local or long-distance calls.
If it is an inside call, the exchange is replaced by the PBX Inside Prefix.
But if the PBX has more than one exchange, a single fixed PBX Inside Prefix is
probably not sufficient. For example, at Columbia University, we must dial
3-xxxx for an internal call to 853-xxxx, but 4-xxxx for a call to 854-xxxx.
That is, the inside prefix is the final digit of the exchange we are dialing.
For this reason, C-Kermit 7.0 provides a method to determine the inside prefix
dynamically at dialing time, consisting of a new variable and new syntax for
the SET DIAL PBX-INSIDE-PREFIX command:
v(d$px)
This variable contains the exchange that was matched when a PBX internal
call was detected. For example, if the PBX exchange list is "853 854"
and a call is placed to +1 (212) 854-9999, v(d$px) is set to 854.
SET DIAL PBX-INSIDE-PREFIX fxxx(...)
If the PBX Inside Prefix is defined to be a function, its evaluation is
deferred until dialing time. Normally, this would be a string function
having v(d$px) as an operand. Of course, you can still specify a constant
string, as before.
So given the following setup:
SET DIAL COUNTRY-CODE 1
SET DIAL AREA-CODE 212
SET DIAL PBX-OUTSIDE-PREFIX 93,
SET DIAL PBX-EXCHANGE 853 854
SET DIAL PBX-INSIDE-PREFIX fright(v(d$px),1)
The following numbers give the results indicated:
Number Result
+1 (212) 854-9876 4-9876
+1 (212) 853-1234 3-1234
+1 (212) 765-4321 93,765-4321
+1 (333) 765-4321 93,1333765-4321
Furthermore, the K_PBX_XCH environment variable may now be set to a list of
exchanges to automatically initialize C-Kermit's PBX exchange list, for
example (in UNIX ksh or bash):
export K_PBX_XCH="853 854"
(Quotes required because of the space.) Of course, this variable can also be
set to a single exchange, as before:
export K_PBX_XCH=853
2.1.13. The DIAL macro - Last-Minute Phone Number Conversions
After a DIAL or LOOKUP command is given, a list of phone numbers is assembled
from the dialing directory (if any), with all location-dependent conversion
rules applied as described in Chapter 5 of "Using C-Kermit".
However, additional conversions might still be required at the last minute
based on local or ephemeral conditions. So that you can have the final word
on the exact format of the dial string, C-Kermit 7.0 lets you pass the
converted string through a macro of your own design for final processing
before dialing. The relevant command is:
SET DIAL MACRO [ name ]
Specifies the name of a macro to be run on each phone number after all
built-in conversions have been applied, just before the number is dialed.
If no name is given, no macro is run. The phone number, as it would have
been dialed if there were no dial macro, is passed to the macro.
The dial macro can do anything at all (except start a file transfer).
However, the normal use for the macro would be to modify the phone number.
For this reason the phone number is passed to the macro as argument number 1
(%1). To cause a modified number to be dialed, the macro should terminate
with a RETURN statement specifying a return value. To leave the number alone,
the macro should simply end. Example:
define xxx return 10108889999$%1
set dial macro xxx
dial xyzcorp
This defines a DIAL MACRO called xxx, which puts an access code on the
front of the number. Another example might be:
def xxx if equal "v(modem)" "hayes-1200" return freplace(%1,$,{,,,,,})
set dial macro xxx
dial xyzcorp
which replaces any dollar-sign in the dial string by a series of five commas,
e.g. because this particular modem does not support the "wait for bong"
feature (remember that commas that are to be included literally in function
arguments must be enclosed in braces to distinguish them from the commas that
separate the arguments) and when the IF condition is not satisfied, the macro
does not return a value, and so the number is not modified. Then when a DIAL
command is given referencing a dialing directory entry, "xyzcorp". The macro
is automatically applied to each matching number.
Numerous dial-, modem-, communications-, and time-related variables are
available for decision making your dial macro. Type SHOW VARIABLES for a
list. Of particular interest is the v(dialcount) variable, which tells how
many times the DIAL command gone through its retry loop: 1 on the first try,
2 on the second, 3 on the third, and so on, and the v(dialresult) and
v(dialstatus) variables.
Here are some other applications for the DIAL MACRO (from users):
. Phone numbers in the dialing directory are formatted with '-'
for readability, but some modems don't like the hyphens, so the DIAL
macro is used to remove them before dialing; e.g 0090-123-456-78-99
becomes 00901234567899: "def xxx return freplace(%1,-)".
. To set some specific modem (or other) options depending on the called
customer or telephone number.
. Choosing the most appropriate provider based on (e.g.) time of day,
or cycling through a list of providers in case some providers might
be busy.
To illustrate the final item, suppose you have a choice among many phone
service providers; the provider is chosen by dialing an access code before the
number. Different providers might be better (e.g. cheaper) for certain times
of day or days of the week, or for dialing certain locations; you can use the
DIAL macro to add the access for the most desirable provider.
Similarly, when the same number might be reached through multiple providers,
it's possible that one provider might not be able to complete the call, but
another one can. In that case, you can use the DIAL macro to switch providers
each time through the DIAL loop -- that's where the v(dialcount) variable
comes in handy.
The following command can be used to debug the DIAL macro:
SET DIAL TEST { ON, OFF }
Normally OFF, so the DIAL command actually dials. When ON, the DIAL
command performs all lookups and number conversions, and then goes through
the number list and retry loop, but instead of actually dialing, lists
the numbers it would have called if none of the DIAL attempts succeeded
(or more precisely, every number was always busy).
2.1.14. Automatic Tone/Pulse Dialing Selection
SET DIAL METHOD { AUTO, DEFAULT, PULSE, TONE }
Chooses the dialing method for subsequent calls.
Prior to version 7.0, C-Kermit's DIAL METHOD was DEFAULT by default, meaning
it does not specify a dialing method to the modem, but relies on the modem
to have an appropriate default dialing method set. So, for example, when
using Hayes compatible modems, the dial string would be something like
ATD7654321, rather than ATDT7654321 or ATDP7654321.
In C-Kermit 7.0 and K95 1.1.18, the dial method can be set from the
environment variable:
K_DIAL_METHOD
when Kermit starts. The values can be TONE, PULSE, or DEFAULT, e.g. (UNIX):
set K_DIAL_METHOD=TONE; export K_DIAL_METHOD
In the absence of a K_DIAL_METHOD definition, the new default SET DIAL METHOD
is AUTO rather than DEFAULT. When DIAL METHOD is AUTO and the local country
code is known, then if tone dialing is universally available in the
corresponding area, tone dialing is used; if dialing from a location where
pulse dialing is mandatory, pulse dialing is used.
The "tone country" and "pulse country" lists are preloaded according to our
knowledge at the time of release. You can see their contents in the SHOW
DIAL listing. You can change the lists with:
SET DIAL TONE-COUNTRIES [ cc [ cc [ ... ] ] ]
Replaces the current TONE-COUNTRIES list with the one given. Each cc is
a country code; separate them with spaces (not commas). Example:
set dial tone-countries 1 358 44 46 49
If no country codes are given, the current list, if any, is removed, in
which case SET DIAL METHOD AUTO is equivalent to SET DIAL METHOD DEFAULT.
SET DIAL PULSE-COUNTRIES [ cc [ cc [ ... ] ] ]
Replaces the current PULSE-COUNTRIES list with the one give. Syntax and
operation is like SET DIAL TONE-COUNTRIES.
If the same country code appears in both lists, Pulse takes precedence.
The SET DIAL TONE- and PULSE-COUNTRIES commands perform no verification
whatsoever on the cc's, since almost any syntax might be legal in some
settings. Furthermore, there is no facility to edit the lists; you can only
replace the whole list. However, since the only purpose of these lists is to
establish a basis for picking tone or pulse dialing automatically, all you
need to override the effect of the list is to set a specific dialing method
with SET DIAL METHOD TONE or SET DIAL METHOD PULSE.
2.1.15. Dial-Modifier Variables
As of C-Kermit 7.0, dial modifiers are available in the following variables:
v(dm_lp) Long pause
v(dm_sp) Short pause
v(dm_pd) Pulse dial
v(dm_td) Tone dial
v(dm_wa) Wait for answer
v(dm_wd) Wait for dialtone
v(dm_rc) Return to command mode
You can use these in your dial strings in place of hardwired modifiers like
"@", ",", etc, for increased portability of scripts. Example:
C-Kermit>set modem type usrobotics
C-Kermit>sho variables dm
v(dm_lp) = ,
v(dm_sp) = /
v(dm_pd) = P
v(dm_td) = T
v(dm_wa) = @
v(dm_wd) = W
v(dm_rc) = ;
C-Kermit>exit
2.1.16. Giving Multiple Numbers to the DIAL Command
Prior to C-Kermit 7.0, the only way to give a DIAL command a list of phone
numbers to try until one answers was to create a dialing directory that had
multiple entries under the same name, and then use that entry name in the DIAL
command. Now a list of numbers can be given to the DIAL command directly in
the following format:
dial {{number1}{number2}{number3}...}
This is the same list format used by SEND /EXCEPT: and other commands that
allow a list where normally a single item is given. Restrictions on this
form of the DIAL command are:
. The first two braces must be adjacent; spacing is optional thereafter.
. Each number must be an actual number to dial, not a dialing directory entry.
. Dialing directory entries may not contain number lists in this format.
In all other respects, the numbers are treated as if they had been fetched
from the dialing directory; they can be in literal or portable format, etc.
Example:
dial {{7654321} {+1 (212) 5551212} { 1-212-5556789 }}
The list can be any length at all, within reason.
This feature is especially handy for use with the K95 Dialer, allowing a list
of phone numbers to be specified in the Telephone Number box without having
to set up or reference a separate dialing directory.
You can also use it to add commonly-dialed sequences as variables in your
C-Kermit customization file, e.g.:
define work {{7654321}{7654322}{7654323}}
and then:
dial {m(work)}
(the variable name must be enclosed in braces).
Or more simply:
define work dial {{7654321}{7654322}{7654323}}
and then:
work
2.2. Modems
2.2.1. New Modem Types
Since C-Kermit 6.0:
atlas-newcom-33600ifxC Atlas/Newcom 33600
att-keepintouch AT&T KeepinTouch PCMCIA V.32bis Card Modem
att-1900-stu-iii AT&T Secure Data STU-III Model 1900
att-1910-stu-iii AT&T Secure Data STU-III Model 1910
bestdata Best Data
cardinal Cardinal V.34 MVP288X series.
compaq Compaq Data+Fax (e.g. in Presario)
fujitsu Fujitsu Fax/Modem Adapter
generic-high-speed Any modern error-correcting data-compressing modem
itu-t-v25ter/v250 ITU-T (CCITT) V.25ter (V.250) standard command set
megahertz-att-v34 Megahertz AT&T V.34
megahertz-xjack Megahertz X-Jack
motorola-codex Motorola Codex 326X Series
motorola-montana Motorola Montana
mt5634zpx Multitech MT5634ZPX
rockwell-v90 Rockwell V.90 56K
rolm-244pc Siemens/Rolm 244PC (AT command set)
rolm-600-series Siemens/Rolm 600 Series (AT command set)
spirit-ii QuickComm Spirit II
suprasonic SupraSonic V288+
supra-express-v90 Supra Express V.90
One of the new types, "generic-high-speed" needs a bit of explanation. This
type was added to easily handle other types that are not explicitly covered,
without going through the bother of adding a complete user-defined modem type.
This one works for modern modems that use the AT command set, on the
assumption that all the default ("factory") settings of the modem (a) are
appropriate for Kermit, (b) include error correction, data compression,
and speed buffering; and (c) are recallable with the command AT&F.
If the command to recall your modem's profile is not AT&F, use the SET MODEM
COMMAND INIT-STRING command to specify the appropriate modem command. The
default init-string is AT&F13 (that is, AT, ampersand, F, and then carriage
return); a survey of about 20 modern modem types shows they all support this,
but they might mean different things by it. For example, the USR Sportster or
Courier needs AT&F1 (not AT&F, which is equivalent to AT&F0, which recalls an
inappropriate profile), so for USR modems:
set modem type generic-high-speed
set modem command init AT&F113
Of course, USR modems already have their own built-in modem type. But if you
use this one instead, it will dial faster because it has fewer commands to
give to the modem; in that sense "&F1" is like a macro that bundles numerous
commands into a single one. See your modem manual for details about factory
profiles and commands to recall them.
WARNING: Do not use the generic-high-speed modem type in operating systems
like VMS where hardware flow control is not available, at least not unless you
change the init string from AT&F13 to something else that enables local
Xon/Xoff or other appropriate type of flow control.
Also see Section 2.1.7 for additional hints about making dialing go faster.
2.2.2. New Modem Controls
SET MODEM CAPABILITIES <list>
In C-Kermit 7.0, this command automatically turns MODEM SPEED-MATCHING OFF
if SB (Speed Buffering) is in the <list>, and turns it ON if SB is absent.
SET MODEM COMMAND PREDIAL-INIT [ <text> ]
Commands to be sent to the modem just prior to dialing. Normally none.
SET MODEM SPEAKER { ON, OFF }
Determines whether modem speaker is on or off while call is being placed.
ON by default. Note: This command does not provide fine-grained control
over when the speaker is on or off. Normally, ON means while the call is
being placed, until the point at which carrier is successfully established.
If your modem has a different speaker option that you want to choose, then
use the SET MODEM COMMAND SPEAKER ON <text> command to specify this option.
SET MODEM COMMAND SPEAKER { ON, OFF } [ <text> ]
Specify or override the commands to turn your modem's speaker on and off.
SET MODEM VOLUME { LOW, MEDIUM, HIGH }
When MODEM SPEAKER is on, select volume. Note: In some modems, especially
internal ones, these commands have no effect; this is a limitation of the
particular modem, not of Kermit.
SET MODEM COMMAND VOLUME { LOW, MEDIUM, HIGH } [ <text> ]
Specify or override the commands to set your modem's speaker volume.
SET MODEM COMMAND IGNORE-DIALTONE [ <text> ]
The command to enable blind dialing (section 2.1.6).
SET MODEM ESCAPE-CHARACTER <code>
Has been augmented to allow codes of 0 or less:
< 0 means the escape mechanism is disabled.
= 0 means to use (restore) the default value from the modem database.
> 0 and < 128 is a literal value to be used instead of the default one.
> 127 means the escape mechanism is disabled.
This affects "modem hangup". When the escape mechanism is disabled, but
SET MODEM HANGUP-METHOD is MODEM-COMMAND, it sends the hangup command
immediately, without the <pause>+++<pause> business first. This is useful
(for example) when sending lots of numeric pages, a process in which we
never go online, and so never need to escape back. Eliminating the
unnecessary pauses and escape sequence allows a lot more pages to be sent
per unit time.
Recall that C-Kermit can dial modems to which it is connected via TCP/IP
(Telnet or Rlogin) as described on page 126 of "Using C-Kermit", 2nd Ed.
In this case the MODEM HANGUP-METHOD should be MODEM-COMMAND, since RS-232
signals don't work over TCP/IP connections. As noted in the manual, such
connections are set up by the following sequence:
set host <host> [ <port> ]
set modem type <name>
dial <number>
But this can cause complications when you use Kermit to switch between serial
and TCP/IP connections. In the following sequence:
set host <name>
set modem type <name>
set port <name>
the first two commands obey the rules for dialing out over Telnet. However,
the SET PORT command requires that Kermit close its current (Telnet)
connection before it can open the serial port (since Kermit can only have one
connection open at a time). But since a modem type was set after the "set
host" command was given, Kermit assumes it is a Telnet dialout connection and
so sends the modem's hangup sequence is sent to the Telnet host. To avoid
this, close the network connection explicitly before opening the serial one:
set host <name>
close
set modem type <name>
set port <name>
2.3. TELNET and RLOGIN
For additional background, please also read the TELNET.TXT file.
Cautions:
If making a Telnet connection with C-Kermit takes a very long time, like
over a minute, whereas the system Telnet program makes the same connection
immediately, try including the /NOWAIT switch:
C-Kermit> telnet /nowait hostname
See TELNET.TXT for details. If it also takes a very long time to make a
Telnet connection with system Telnet, then the delay is most likely caused
by reverse DNS lookups when your host is not properly registered in DNS.
When supplying numeric IP addresses to C-Kermit or to any other application
(regular Telnet, Rlogin, etc), do not include leading 0's in any fields unless
you intend for those fields to be interpreted as octal (or hex) numbers. The
description of the Internet address interpreter (the sockets library
inet_addr() routine) includes these words:
All numbers supplied as "parts" in a "." notation may be decimal, octal,
or hexadecimal, as specified in the C language (that is, a leading 0x or
0X implies hexadecimal; otherwise, a leading 0 implies octal; otherwise,
the number is interpreted as decimal).
To illustrate, 128.59.39.2 and 128.059.039.002 are NOT the same host! Even
though most of the fields contain non-octal digits. Using system Telnet (not
Kermit):
$ telnet 128.059.039.002
Trying 128.49.33.2 ...
Of course the same thing happens with Kermit because it uses (as it must) the
same system service for resolving network addresses that Telnet, FTP, and all
other TCP/IP applications use.
The RLOGIN section on page 123 does not make it clear that you can use the
SET TELNET TERMINAL-TYPE command to govern the terminal type that is reported
by C-Kermit to the RLOGIN server.
Note that the SET TCP commands described on pages 122-123 might be absent;
some platforms that support TCP/IP do not support these particular controls.
New commands:
TELOPT { AO, AYT, BREAK, CANCEL, EC, EL, EOF, EOR, GA, IP, DMARK, DO, DONT,
NOP, SB, SE, SUSP, WILL, WONT }
This command was available previously, but supported only DO, DONT, WILL,
and WONT. Now it lets you send all the Telnet protocol commands. Note
that certain commands do not require a response, and therefore can be used
as nondestructive "probes" to see if the Telnet session is still open; e.g.:
set host xyzcorp.com
...
telopt nop
if fail stop 1 Connection lost
SET TCP ADDRESS [ <ip-address> ]
Specifies the IP address of the computer that C-Kermit is running on.
Normally this is not necessary. The exception would be if your
machine has multiple network adapters (physical or virtual) with a
different address for each adapter AND you want C-Kermit to use a
specific address when making outgoing connections or accepting
incoming connections.
SET TCP DNS-SERVICE-RECORDS {ON, OFF}
Tells C-Kermit whether to try to use DNS SRV records to determine the
host and port number upon which to find an advertised service. For
example, if a host wants regular Telnet connections redirected to some
port other than 23, this feature allows C-Kermit to ask the host which
port it should use. Since not all domain servers are set up to answer
such requests, this feature is OFF by default.
SET TCP REVERSE-DNS-LOOKUP { ON, OFF, AUTO }
Tells Kermit whether to perform a reverse DNS lookup on TCP/IP connections.
This allows Kermit to determine the actual hostname of the host it is
connected to, which is useful for connections to host pools, and is required
for Kerberos connections to host pools and for incoming connections. If the
other host does not have a DNS entry, the reverse lookup could take a long
time (minutes) to fail, but the connection will still be made. Turn this
option OFF for speedier connections if you do not need to know exactly which
host you are connected to and you are not using Kerberos. AUTO, the
default, means the lookup is done on hostnames, but not on numeric IP
addresses.
SET TELNET WAIT-FOR-NEGOTIATIONS { ON, OFF }
Each Telnet option must be fully negotiated either On or Off before the
session can continue. This is especially true with options that require
sub-negotiations such as Authentication, Encryption, and Kermit; for
proper support of these options Kermit must wait for the negotiations to
complete. Of course, Kermit has no way of knowing whether a reply is
delayed or not coming at all, and so will wait a minute or more for
required replies before continuing the session. If you know that Kermit's
Telnet partner will not be sending the required replies, you can set this
option of OFF to avoid the long timeouts. Or you can instruct Kermit to
REFUSE specific options with the SET TELOPT command.
SET TELOPT [ { /CLIENT, /SERVER } ] <option> -
{ ACCEPTED, REFUSED, REQUESTED, REQUIRED } -
[ { ACCEPTED, REFUSED, REQUESTED, REQUIRED } ]
SET TELOPT lets you specify policy requirements for Kermit's handling of
Telnet option negotiations. Setting an option is REQUIRED causes Kermit
to offer the option to the peer and disconnect if the option is refused.
REQUESTED causes Kermit to offer an option to the peer. ACCEPTED results
in no offer but Kermit will attempt to negotiate the option if it is
requested. REFUSED instructs Kermit to refuse the option if it is
requested by the peer.
Some options are negotiated in two directions and accept separate policies
for each direction; the first keyword applies to Kermit itself, the second
applies to Kermit's Telnet partner; if the second keyword is omitted, an
appropriate (option-specific) default is applied. You can also include a
/CLIENT or /SERVER switch to indicate whether the given policies apply
when Kermit is the Telnet client or the Telnet server; if no switch is
given, the command applies to the client.
Note that some of Kermit's Telnet partners fail to refuse options that
they do not recognize and instead do not respond at all. In this case it
is possible to use SET TELOPT to instruct Kermit to REFUSE the option
before connecting to the problem host, thus skipping the problematic
negotiation.
Use SHOW TELOPT to view current Telnet Option negotiation settings.
SHOW TELNET displays current Telnet settings.
2.3.0. Bug Fixes
If "set host nonexistent-host" was given (and it properly failed), followed by
certain commands like SEND, the original line and modem type were not restored
and C-Kermit thought that it still had a network hostname; fixed in 7.0.
2.3.1. Telnet Binary Mode Bug Adjustments
SET TELNET BUG BINARY-ME-MEANS-U-TOO { ON, OFF } was added to edit 192
after the book was printed. Also SET TELNET BUG BINARY-U-MEANS-ME-TOO.
The default for both is OFF. ON should be used when communicating with a
Telnet partner (client or server) that mistakenly believes that telling
C-Kermit to enter Telnet binary mode also means that it, too, is in binary
mode, contrary to the Telnet specification, which says that binary mode must
be negotiated in each direction separately.
2.3.2. VMS UCX Telnet Port Bug Adjustment
A new command, SET TCP UCX-PORT-BUG, was added for VMS versions with UCX (DEC
TCP/IP), applying only to early versions of UCX, like 2.2 or earlier. If you
try to use VMS C-Kermit to make a Telnet connection using a port name (like
"telnet", which is used by default), the underlying UCX getservbyname()
function might return the service number with its bytes swapped and the
connection will fail. If "telnet hostname 23" works, then your version of UCX
has this bug and you can put "set tcp ucx-port-bug on" in your CKERMIT.INI
file to get around it.
2.3.3. Telnet New Environment Option
The TELNET NEW-ENVIRONMENT option (RFC1572) is supported as 7.0. This option
allows the C-Kermit Telnet client to send certain well-known variables to the
Telnet server, including USER, PRINTER, DISPLAY, and several others. This
feature is enabled by default in Windows and OS/2, disabled by default
elsewhere. The command to enable and disable it is:
SET TELNET ENVIRONMENT { ON, OFF }
When ON, and you Telnet to another computer, you might (or might not) notice
that the "login:" or "Username:" prompt does not appear -- that's because your
username was sent ahead, in which case the remote system might prompt you only
for your password (similar to Rlogin). Use "set telnet environment off" to
defeat this feature, particularly in scripts where the dialog must be
predictable. You can also use this command to specify or override specific
well-known environment variable values:
SET TELNET ENVIRONMENT { ACCT,DISPLAY,JOB,PRINTER,SYSTEMTYPE,USER } [ <text> ]
2.3.4. Telnet Location Option
The TELNET LOCATION option (RFC779) is supported in 7.0. This option allows
the C-Kermit Telnet client to send a location string to the server if the
server indicates its willingness to accept one. If an environment variable
named LOCATION exists at the time C-Kermit starts, its value is used as the
location string. If you want to change it, use:
SET TELNET LOCATION <text>
If you omit the <text> from this command, the Telnet location feature is
disabled.
SET TELNET ENVIRONMENT DISPLAY is used to set the DISPLAY variable that is
sent to the host, as well as the the XDISPLAY location.
2.3.5. Connecting to Raw TCP Sockets
The SET HOST and TELNET commands now accept an optional switch, /RAW-SOCKET,
at the end, only if you first give a host and a port. Example:
set host xyzcorp.com 23 /raw-socket
set host 128.49.39.2:2000 /raw-socket
telnet xyzcorp.com 3000 /raw
Without this switch, C-Kermit behaves as a Telnet client when (a) the port is
23 or 1649, or (b) the port is not 513 and the server sent what appeared to be
Telnet negotiations -- that is, messages starting with 0xFF (IAC). With this
switch, Kermit should treat all incoming bytes as raw data, and will not
engage in any Telnet negotiations or NVT CRLF manipulations. This allows
transparent operation through (e.g.) raw TCP ports on Cisco terminal servers,
through the 'modemd' modem server, etc.
2.3.6. Incoming TCP Connections
Accomplished via SET HOST * <port>, were introduced in C-Kermit 6.0, but for
UNIX only. In Version 7.0, they are also available for VMS.
2.4. The EIGHTBIT Command
EIGHTBIT is simply a shorthand for: SET PARITY NONE, SET TERMINAL BYTESIZE 8,
SET COMMAND BYTESIZE 8; that is, a way to set up an 8-bit clean connection
in a single command.
2.5. The Services Directory
Chapter 7 of "Using C-Kermit" does not mention the ULOGIN macro, which is
used by our sample services directory, CKERMIT.KND. Unlike UNIXLOGIN,
VMSLOGIN, etc, this one is for use with systems that require a user ID but
no password. Therefore it doesn't prompt for a password or wait for a
password prompt from the remote service.
In version 7.0, the CALL macro was changed to not execute a SET MODEM TYPE
command if the given modem type was the same as the current one; otherwise the
new SET MODEM TYPE command would overwrite any customizations that the user
had made to the modem settings. Ditto for SET LINE / SET PORT and SET SPEED.
2.6. Closing Connections
Until version 7.0, there was never an obvious and general way to close a
connection. If a serial connection was open, it could be closed by "set
line" or "set port" (giving no device name); if a network connection was
open, it could be closed by "set host" (no host name).
In version 7.0, a new command closes the connection in an obvious and
straightforward way, no matter what the connection type:
CLOSE [ CONNECTION ]
The CLOSE command was already present, and required an operand such as
DEBUG-LOG, WRITE-FILE, etc, and so could never be given by itself. The new
CONNECTION operand is now the default operand for CLOSE, so CLOSE by itself
closes the connection, if one is open, just as you would expect, especially
if you are a Telnet or Ftp user.
Also see the description of the new SET CLOSE-ON-DISCONNECT command in
Section 2.10.
2.7. Using C-Kermit with External Communication Programs
C-Kermit 7.0 includes a new ability to create and conduct sessions through
other communications programs. Two methods are available:
a. Pty (pseudoterminal): The external program is run on a "pseudoterminal",
which is controlled by Kermit. This method works with practically any
external program, but it is not portable. At this writing, it works only
on some (not all) UNIX versions, and not on any non-UNIX platforms.
b. Pipe: The external program's standard input and output are redirected
through a "pipe" controlled by Kermit. This method is relatively
portable -- it should work across all UNIX versions, and it also works
in Windows and OS/2 -- but it is effective only when the external
program actually uses standard i/o (and many don't).
The two methods are started differently but are used the same way thereafter.
The purpose of this feature is to let you use C-Kermit services like file
transfer, character-set translation, scripting, automatic dialing, etc, on
connections that Kermit can't otherwise make itself.
This feature is the opposite of the REDIRECT feature, in which C-Kermit makes
the connection, and redirects an external (local) command or program over this
connection. In a pty or pipe connection, C-Kermit runs and controls a local
command or program, which makes the connection. (The same method can be used
to simply to control a local program without making a connection; see Section
2.8.)
To find out if your version of Kermit includes PTY support, type "show
features" and look for NETPTY in the alphabetical list of options. For pipes,
look for NETCMD.
The commands are:
SET NETWORK TYPE PTY or SET NETWORK TYPE PIPE
SET HOST <command>
where <command> is any interactive command. If the command does not use
standard i/o, you must use SET NETWORK TYPE PTY.
Notes:
a. COMMAND is an invisible synonym for PIPE.
b. The <command> and its arguments are case-sensitive in UNIX.
The SET NETWORK TYPE, SET HOST sequence sets the given network type for all
subsequent SET HOST commands until another SET NETWORK TYPE command is given
to change it.
You can also use the new /NETWORK-TYPE:PTY or /NETWORK-TYPE:PIPE (or simply
/PIPE or /PTY) switches on the SET HOST command itself:
SET HOST /NETWORK-TYPE:PIPE <command> ; These two are the same
SET HOST /PIPE <command>
SET HOST /NETWORK-TYPE:PTY <command> ; Ditto
SET HOST /PTY <command>
These are like SET NETWORK TYPE followed by SET HOST, except they apply only
to the connection being made and do not change the global network type setting
(see Section 1.5 about the difference between switches and SET commands).
Include any command-line options with the <command> that might be needed, as
in this example where C-Kermit uses another copy of itself as the
communications program:
SET HOST /PIPE /CONNECT kermit -YQJ xyzcorp.com
As usual, if you include the /CONNECT switch, SET HOST enters CONNECT mode
immediately upon successful execution of the given command. Therefore a new
command is available as a shorthand for SET HOST /CONNECT /PTY:
PTY [ <command> ]
And for SET HOST /CONNECT /PIPE:
PIPE [ <command> ]
Thus, the PTY and PIPE commands work like the TELNET and RLOGIN commands: they
set up the connection (in this case, using the given command) and then enter
CONNECT mode automatically (if the PIPE or PTY command is given without a
<command>, it continues the current session if one is active; otherwise it
gives an error message).
The PIPE command is named after the mechanism by which C-Kermit communicates
with the <command>: UNIX pipes. C-Kermit's i/o is "piped" through the given
command. Here is a typical example:
PIPE rlogin -8 xyzcorp.com
This is equivalent to:
SET HOST /PIPE rlogin -8 xyzcorp.com
CONNECT
and to:
SET HOST /PIPE /CONNECT rlogin -8 xyzcorp.com
IMPORTANT:
If you are writing a script, do not use the PIPE, PTY, TELNET, or RLOGIN
command unless you really want C-Kermit to enter CONNECT mode at that
point. Normally SET HOST is used in scripts to allow the login and
other dialogs to be controlled by the script itself, rather than by
an actively participating human at the keyboard.
Throughput of pty and pipe connections is limited by the performance of the
chosen command or program and by the interprocess communication (IPC) method
used and/or buffering capacity of the pipe or pty, which in turn depends on
the underlying operating system.
In one trial (on SunOS 4.1.3), we observed file transfer rates over an rlogin
connection proceeding at 200Kcps for downloads, but only 10Kcps for uploads on
the same connection with the same settings (similar disparities were noted in
HP-UX). Examination of the logs revealed that a write to the pipe could take
as long as 5 seconds, whereas reads were practically instantaneous. On the
other hand, using Telnet as the external program rather than rlogin, downloads
and uploads were better matched at about 177K each.
Most external communication programs, like C-Kermit itself, have escape
characters or sequences. Normally these begin with (or consist entirely of) a
control character. You must be sure that this control character is not
"unprefixed" when uploading files, otherwise the external program will "escape
back" to its prompt, or close the connection, or take some other unwanted
action. When in CONNECT mode, observe the program's normal interaction rules.
Of course C-Kermit's own escape character (normally Ctrl-) is active too,
unless you have taken some action to disable it.
On PTY connections, the underlying PTY driver is not guaranteed to be
transparent to control characters -- for example, it might expand tabs,
translate carriage returns, generate signals if it sees an interrupt
character, and so on. Similar things might happen on a PIPE connection. For
this reason, if you plan to transfer files over a PTY or PIPE connection, tell
the file sender to:
SET PREFIXING ALL
This causes all control characters to be prefixed and transmitted
as printable ASCII characters.
If the external connection program is not 8-bit clean, you should also:
SET PARITY SPACE
This causes 8-bit data to be encoded in 7 bits using single and/or
locking shifts.
And if it does not make a reliable connection (such as those made by Telnet,
Rlogin, Ssh, etc), you should:
SET STREAMING OFF
This forces C-Kermit to treat the connection as unreliable and
to engage in its normal ACK/NAK protocol for error detection and
correction, rather than "streaming" its packets, as it normally
does on a network connection (Section 4.20).
In some cases, buffer sizes might be restricted, so you might also need to
reduce the Kermit packet length to fit; this is a trial-and-error affair. For
example, if transfers always fail with 4000-byte packets, try 2000. If that
fails too, try 1000, and so on. The commands are:
SET RECEIVE PACKET-LENGTH <number>
This tells the file receiver to tell the file sender the longest
packet length it can accept.
SET SEND PACKET-LENGTH <number>
This tells the file sender not to send packets longer than the given
length, even if the receiver says longer ones are OK. Of course, if
the receiver's length is shorter, the shorter length is used.
If none of this seems to help, try falling back to the bare minimum,
lowest-common-denominator protocol settings:
ROBUST
No sliding windows, no streaming, no control-character unprefixing,
packet length 90.
And then work your way back up by trial and error to get greater throughput.
Note that when starting a PIPE connection, and the connection program (such as
telnet or rlogin) prints some greeting or information messages before starting
the connection, these are quite likely to be printed with a stairstep effect
(linefeed without carriage return). This is because the program is not
connected with the UNIX terminal driver; there's not much Kermit can do about
it. Once the connection is made, everything should go back to normal. This
shouldn't happen on a PTY connection because a PTY is, indeed, a terminal.
On a similar note, some connection programs (like Solaris 2.5 rlogin) might
print lots of error messages like "ioctl TIOCGETP: invalid argument" when
used through a pipe. They are annoying but usually harmless. If you want to
avoid these messages, and your shell allows redirection of stderr, you can
redirect stderr in your pipe command, as in this example where the user's
shell is bash:
PIPE rlogin xyzcorp.com 2> /dev/null
Or use PTY rather than PIPE, since PTY is available on Solaris.
2.7.0. C-Kermit over tn3270 and tn5250
Now you can make a connection from C-Kermit "directly" to an IBM mainframe and
transfer files with it, assuming it has Kermit-370 installed. Because tn3270
is neither 8-bit clean nor transparent to control characters, you must give
these commands:
SET PREFIXING ALL ; Prefix all control characters
SET PARITY SPACE ; Telnet connections are usually not 8-bit clean
and then:
SET HOST /PTY /CONNECT tn3270 abccorp.com
or simply:
pty tn3270 abccorp.com
SET HOST /PIPE does not work in this case, at least not for file transfer.
File transfer does work, however, with SET HOST /PTY, provided you use the
default packet length of 90 bytes; anything longer seems to kill the session.
You can also make connections to IBM AS/400 computers if you have a tn5250
program installed:
pty tn5250 <hostname>
In this case, however, file transfer is probably not in the cards since
nobody has ever succeeded in writing a Kermit program for the AS/400.
Hint:
define tn3270 {
check pty
if fail end 1 Sorry - no PTY support...
pty tn3270 %*
}
Similarly for tn5250. Note that CHECK PTY and CHECK PIPE can be used in
macros and scripts to test whether PTY or PIPE support is available.
2.7.1. C-Kermit over Telnet
Although C-Kermit includes its own Telnet implementation, you might need to
use an external Telnet program to make certain connections; perhaps because it
has access or security features not available in C-Kermit itself. As noted
above, the only precautions necessary are usually:
SET PREFIXING ALL ; Prefix all control characters
SET PARITY SPACE ; Telnet connections might not be 8-bit clean
and then:
SET HOST /PTY (or /PIPE) /CONNECT telnet abccorp.com
or, equivalently:
PTY (or PIPE) telnet abccorp.com
2.7.2. C-Kermit over Rlogin
C-Kermit includes its own Rlogin client, but this can normally be used only if
you are root, since the rlogin TCP port is privileged. But ptys and pipes let
you make rlogin connections with C-Kermit through your computer's external
rlogin program, which is normally installed as a privileged program:
SET PREFIXING ALL
and then:
SET HOST /PTY (or /PIPE) /CONNECT rlogin -8 abccorp.com
or, equivalently:
PTY (or PIPE) rlogin -8 abccorp.com
The "-8" option to rlogin enables transmission of 8-bit data. If this is
not available, then include SET PARITY SPACE if you intend to transfer files.
Note that the normal escape sequence for rlogin is Carriage Return followed by
Tilde (~), but only when the tilde is followed by certain other characters;
the exact behavior depends on your rlogin client, so read its documentation.
2.7.3. C-Kermit over Serial Communication Programs
Ptys and pipes also let you use programs that make serial connections, such as
cu or tip. For example, C-Kermit can be used through cu to make connections
that otherwise might not be allowed, e.g. because C-Kermit is not installed
with the required write permissions to the dialout device and the UUCP
lockfile directory.
Suppose your UUCP Devices file contains an entry for a serial device tty04 to
be used for direct connections, but this device is protected against you (and
Kermit when you run it). In this case you can:
SET CONTROL PREFIX ALL
PTY (or PIPE) cu -l tty04
(Similarly for dialout devices, except then you also need to include the phone
number in the "cu" command.)
As with other communication programs, watch out for cu's escape sequence,
which is the same as the rlogin program's: Carriage Return followed by Tilde
(followed by another character to specify an action, like "." for closing the
connection and exiting from cu).
2.7.4. C-Kermit over Secure Network Clients
DISCLAIMER: There are laws in the USA and other countries regarding
use, import, and/or export of encryption and/or decryption or other
forms of security software, algorithms, technology, and intellectual
property. The Kermit Project attempts to follow all known statutes,
and neither intends nor suggests that Kermit software can or should
be used in any way, in any location, that circumvents any regulations,
laws, treaties, covenants, or other legitimate canons or instruments
of law, international relations, trade, ethics, or propriety.
For secure connections or connections through firewalls, C-Kermit 7.0 can be a
Kerberos, SRP, and/or SOCKS client when built with the appropriate options and
libraries. But other application-level security acronyms and methods -- SSH,
SSL, SRP, TLS -- pop up at an alarming rate and are (a) impossible to keep up
with, (b) usually mutually incompatible, and (c) have restrictions on export
or redistribution and so cannot be included in C-Kermit itself.
However, if you have a secure text-based Telnet (or other) client that employs
one of these security methods, you can use C-Kermit "through" it via a pty
or pipe.
2.7.4.1. SSH
C-Kermit does not and can not incorporate SSH due to licensing, patent,
and USA export law restrictions.
The UNIX SSH client does not use standard input/output, and therefore can be
used only by Kermit's PTY interface, if one is present. The cautions about
file transfer, etc, are the same as for Rlogin. Example:
SET PREFIXING ALL
PTY ssh XYZCORP.COM
Or, for a scripted session:
SET PREFIXING ALL
SET HOST /PTY ssh XYZCORP.COM
Hint:
define ssh {
check pty
if fail end 1 Sorry - no PTY support...
pty ssh %*
}
2.7.4.2. SSL
Secure Sockets Layer (SSL) is another TCP/IP security overlay, this one
designed by and for Netscape. An SSL Telnet client is available for UNIX
from the University of Queensland. More info at:
http://www.psy.uq.oz.au/~ftp/Crypto/
Interoperability with C-Kermit is unknown. C-Kermit also includes its own
built-in SSL/TLS support, but it is not exportable; see the C-Kermit
security.txt file for details.
2.7.4.3. SRP
SRP(TM) is Stanford University's Secure Remote Password protocol. An SRP
Telnet client is available from Stanford:
http://srp.stanford.edu/srp/
Stanford's SRP Telnet client for UNIX has been tested on SunOS and works fine
with C-Kermit, as described in Section 2.7.1, e.g.
SET PREFIX ALL
PTY (or PIPE) srp-telnet xenon.stanford.edu
C-Kermit itself can be built as an SRP Telnet client on systems that have
libsrp.a installed; the C-Kermit support code, however, may not be exported
outside the USA or Canada.
2.7.4.4. SOCKS
C-Kermit can be built as a SOCKS-aware client on systems that have a SOCKS
library. See section 8.1.1 of the ckccfg.txt file.
C-Kermit 7.0 can also be run over SOCKSified Telnet or rlogin clients with SET
NETWORK TYPE COMMAND. Suppose the Telnet program on your system is SOCKS
enabled but C-Kermit is not. Make Kermit connections like this:
SET PREFIX ALL
PTY (or PIPE) telnet zzz.com
2.7.4.5. Kerberos
UNIX C-Kermit can be built with MIT Kerberos IV or V authentication and
encryption. Instructions are available in a separate document, security.txt.
Additional modules are required that can not be exported from the USA to any
country except Canada, by US law.
If you have Kerberos installed but you don't have a Kerberized version of
C-Kermit, you can use ktelnet as C-Kermit's external communications program
to make secure connections without giving up C-Kermit's services:
SET PREFIX ALL
PTY (or PIPE) ktelnet cia.gov
2.8. Scripting Local Programs
If your version of Kermit has PTY support built in, then any text-based
program can be invoked with SET HOST /PTY or equivalent command and controlled
using the normal sequence of OUTPUT, INPUT, IF SUCCESS commands (this is the
same service that is provided by the 'expect' program, but controlled by the
Kermit script language rather than Tcl).
When PTY service is not available, then any program that uses standard input
and output can be invoked with SET HOST /PIPE.
Here's an example in which we start an external Kermit program, wait for its
prompt, give it a VERSION command, and then extract the numeric version number
from its response:
set host /pty kermit -Y
if fail stop 1 {Can't start external command}
input 10 C-Kermit>
if fail stop 1 {No C-Kermit> prompt}
output version13
input 10 {Numeric: }
if fail stop 1 {No match for "Numeric:"}
clear input
input 10 10
echo VERSION = "fsubstr(v(input),1,6)"
output exit13
This technique could be used to control any other interactive program, even
those that do screen formatting (like Emacs or Vi), if you can figure out the
sequence of events. If your Kermit program doesn't have PTY support, then the
commands are restricted to those using standard i/o, including certain shells,
interactive text-mode "hardcopy" editors like ex, and so on.
If you are using the PTY interface, you should be aware that it runs the
given program or command directly on the pty, without any intervening shell
to interpret metacharacters, redirectors, etc. If you need this sort of
thing, include the appropriate shell invocation as part of your command; for
example:
pty echo *
just echoes "*"; whereas:
pty ksh -c "echo *"
echoes all the filenames that ksh finds matching "*".
Similarly for redirection:
set host /pty ksh -c "cat > foo" ; Note: use shell quoting rules here
set transmit eof 4
transmit bar
And for that matter, for built-in shell commands:
set host /pty ksh -c "for i in *; do echo $i; done"
The PIPE interface, on the other hand, invokes the shell automatically, so:
pipe echo *
prints filenames, not "*".
2.9. X.25 Networking
X.25 networking is documented in "Using C-Kermit", 2nd Edition. When the book
was published, X.25 was available only in SunOS, Solaris, and Stratus VOS.
Unlike TCP/IP, X.25 APIs are not standardized; each vendor's X.25 libraries
and services (if they have them at all) are unique.
This section describes new additions.
2.9.1. IBM AIXLink/X.25 Network Provider Interface for AIX
Support for X.25 was added via IBM's Network Provider Interface (NPI),
AIXLink/X.25 1.1, to the AIX 4.x version of C-Kermit 7.0. Unfortunately,
AIXLink/X.25 is a rather bare-bones facility, lacking in particular any form
of PAD support (X.3, X.28, X.29). Thus, the AIX version of C-Kermit, when
built to include X.25 networking, has neither a PAD command, nor a SET PAD
command. The same is true for the underlying AIX system: no PAD support.
Thus it is not possible to have an interactive shell session over an X.25
connection into an AIX system (as far as we know), even from X.25-capable
Kermit versions (such as Solaris or VOS) that do include PAD support.
Thus the X.25 capabilities in AIX C-Kermit are limited to peer-to-peer
connections, e.g. from a C-Kermit client to a C-Kermit server. Unlike the
Solaris, SunOS, and VOS versions, the AIX version can accept incoming X.25
connections:
set network type x.25
if fail stop 1 Sorry - no X.25 support
; Put any desired DISABLE or ENABLE or SET commands here.
set host /server *
if fail stop 1 X.25 "set host *" failed
And then access it from the client as follows:
set network type x.25
if fail stop 1 Sorry - no X.25 support
set host xxxxxxx ; Specify the X.25/X.121 address
if fail stop 1 Can't open connection
And at this point the client can use the full range of client commands:
SEND, GET, REMOTE xxx, FINISH, BYE.
The AIX version also adds two new variables:
v(x25local_nua) The local X.25 address.
v(x25remote_nua) The X.25 address of the host on the other end
of the connection.
C-Kermit's AIX X.25 client has not been tested against anything other than
a C-Kermit X.25 server on AIX. It is not known if it will interoperate with
C-Kermit servers on Solaris, SunOS, or VOS.
To make an X.25 connection from AIX C-Kermit, you must:
set x25 call-user-data xxxx
where xxxx can be any even-length string of hexadecimal digits, e.g. 123ABC.
2.9.2. HP-UX X.25
Although C-Kermit presently does not include built-in support for HP-UX X.25,
it can still be used to make X.25 connections as follows: start Kermit and
tell it to:
set prefixing all
set parity space
pty padem <address>
This should work in HP-UX 9.00 and later (see Section 2.7). If you have an
earlier HP-UX version, or the PTY interface doesn't work or isn't available,
try:
set prefixing all
set parity space
pipe padem <address>
Failing that, use Kermit to telnet to localhost and then after logging back
in, start padem as you would normally do to connect over X.25.
2.10. Additional Serial Port Controls
C-Kermit 7.0 adds the following commands for greater control over serial
ports. These commands are available only in C-Kermit versions whose
underlying operating systems provide the corresponding services (such as
POSIX and UNIX System V), and even then their successful operation depends
on the capabilities of the specific device and driver.
SET DISCONNECT { ON, OFF }
On a SET LINE or SET PORT connection with SET CARRIER ON or AUTO, if
the carrier signal drops during the connection, indicating that the
connection has been lost, and C-Kermit notices it, this setting governs
what happens next. With SET DISCONNECT OFF, which is consistent with
previous behavior, and therefore the default, C-Kermit continues to keep the
device open and allocated. With SET DISCONNECT ON, C-Kermit automatically
closes and releases the device when it senses a carrier on-to-off
transition, thus allowing others to use it. However, it remains the default
device for i/o (DIAL, REDIAL, INPUT, SEND, CONNECT, etc), so if a subsequent
i/o command is given, the device is reopened if it is still available. When
it has been automatically closed in this manner, SHOW COMMUNICATIONS puts
"(closed)" after its name, and in UNIX, the lockfile disappears -- both from
SHOW COMM and from the lockfile directory itself. Synonym:
SET CLOSE-ON-DISCONNECT.
SET EXIT ON-DISCONNECT { ON, OFF }
Like DISCONNECT, but makes the program exit if a connection drops.
Note that SET CLOSE-ON-DISCONNECT and SET EXIT ON-DISCONNECT apply only to
connections that drop; they do not apply to connections that can't be made
in the first place. For example, they have no effect when a SET LINE,
SET HOST, TELNET, or DIAL command fails.
HANGUP
If [CLOSE-ON-]DISCONNECT is ON, and the HANGUP command is given on a serial
device, and the carrier signal is no longer present after the HANGUP
command, the device is closed and released.
SET PARITY HARDWARE { EVEN, ODD }
Unlike SET PARITY { EVEN, ODD, MARK, SPACE }, which selects 7 data bits
plus the indicated kind of parity (to be done in software by Kermit itself),
SET PARITY HARDWARE selects 8 data bits plus even or odd parity, to be done
by the underlying hardware, operating system, or device driver. This
command is effective only with a SET LINE or SET PORT device. That is, it
has no effect in remote mode, nor on network connections. There is
presently no method for selecting 8 data bits plus mark or space parity.
If hardware parity is in effect, the variable v(hwparity) is set to
"even" or "odd". Note: some platforms might also support settings of
SPACE, MARK, or NONE.
SET STOP-BITS { 1, 2 }
This tells the number of 1-bits to insert after an outbound character's
data and parity bits, to separate it from the next character. Normally 1.
Choosing 2 stop bits should do no harm, but will slow down serial
transmission by approximately 10 percent. Historically, 2 stop bits were
used with Teletypes (at 110 bps or below) for print-head recovery time.
There is presently no method for choosing any number of stop bits besides
1 and 2.
SET SERIAL [ <dps> ]
<dps> stands for Data-bits, Parity, Stop-bits. This is the notation
familiar to many people for serial port configuration: 7E1, 8N1, 7O2, etc.
The data bits number also becomes the TERMINAL BYTESIZE setting. The second
character is E for Even, O for Odd, M for Mark, S for Space, or N for None.
The list of available options depends on the capabilities of the specific
platform. If <dps> is omitted, 8N1 is used. Type "set serial ?" for a
list of available choices. Examples:
SET SERIAL 7E1
Equivalent to SET PARITY EVEN, SET STOP-BITS 1, SET TERM BYTE 7.
SET SERIAL 8N1
Equivalent to SET PARITY NONE, SET STOP-BITS 1, SET TERM BYTE 8.
SET SERIAL 7E2
Equivalent to SET PARITY EVEN and SET STOP-BITS 2, SET TERM BYTE 7.
SET SERIAL 8E2
Same as SET PARITY HARDWARE EVEN, SET STOP-BITS 2, SET TERM BYTE 8.
SET SERIAL
Same as SET PARITY NONE and SET STOP-BITS 1, SET TERM BYTE 8.
Notes:
. The SET SERIAL xx2 options are available only in Kermit versions where the
SET PARITY HARDWARE command is also available. (SHOW FEATURES includes
"HWPARITY" in its options list.)
. The SET SERIAL 7xx and 8N1 options affect the software parity setting, even
for network connections.
. As noted in the manual, selecting 8 data bits does not give you 8-bit
terminal sessions in CONNECT mode unless you also SET TERMINAL BYTESIZE 8.
The default terminal bytesize remains 7, to protect against the situation
where the remote host is generating parity but you don't know about it. If
the terminal bytesize was 8 by default and you CONNECTed to such a host,
you would see only garbage on your screen.
. If you do not give a SET STOP-BITS or SET SET SERIAL command, C-Kermit
does not attempt to set the device's stop bits; instead, it uses whatever
setting the device uses when not given explicit instructions about stop
bits.
SHOW COMMUNICATIONS displays the current settings. Stop bits and hardware
parity are shown only for SET PORT / SET LINE (serial) devices, since they
do not apply to network connections or to remote mode. STOP-BITS is shown
as "(default)" if you have not given an explicit SET STOP-BITS or SET SERIAL
command.
The v(serial) variable shows the SET SERIAL setting (8N1, 7E1, etc).
2.11. Getting Access to the Dialout Device
This section is for UNIX only; note the special words about QNX
at the end. Also see Section 2.0 for SET LINE switches, particularly
the /SHARE switch for VMS only.
C-Kermit does its best to obey the UUCP lockfile conventions of each platform
(machine, operating system, OS version) where it runs, if that platform uses
UUCP.
But simply obeying the conventions is often not good enough, due to the
increasing likelihood that a particular serial device might have more than one
name (e.g. /dev/tty00 and /dev/term/00 are the same device in Unixware 7;
/dev/cua and /dev/cufa are the same device in NeXTSTEP), plus the increasingly
widespread use of symlinks for device names, such as /dev/modem.
C-Kermit 7.0 goes to greater lengths than previous versions to successfully
interlock with other communications program (and other instances of Kermit
itself); for example, by:
. Creation of dual lockfiles whenever a symlink is used; one for the link
name and one for the "real" name as revealed by readlink().
. Creation of dual lockfiles in HP-UX according to HP rules.
. Creation of dual uppercase/lowercase lockfile names in SCO UNIX/ODT/OSR5.
. The use of ttylock() in versions of AIX where it works.
. The use, wherever possible, of lockfile names based on inode/major/minor
device number rather than device name.
See the ckuins.txt and ckubwr.txt files for details.
QNX is almost unique among UNIX varieties in having no UUCP programs nor
UUCP-oriented dialout-device locking conventions. QNX does, however, allow a
program to get the device open count. This can not be a reliable form of
locking unless all applications do it (and they don't), so by default, Kermit
uses this information only for printing a warning message such as:
C-Kermit>set line /dev/ser1
WARNING - "/dev/ser1" looks busy...
However, if you want to use it as a lock, you can do so with:
SET QNX-PORT-LOCK { ON, OFF }
QNX-PORT-LOCK is OFF by default; if you set in ON, C-Kermit fails to open
any dialout device when its open count indicates that another process has it
open. SHOW COMM (in QNX only) displays the setting, and if you have a port
open, it also shows the current open count (with C-Kermit's own access
always counting as 1).
2.12. The Connection Log
C-Kermit 7.0 adds the ability to log connections, so you can see where you've
been and have a record of calls you've made. A connection is defined as any
communications session that is begun by SET LINE, SET PORT, DIAL, SET HOST,
TELNET, or RLOGIN. Connections are not logged unless you request it; the
command is:
LOG CX [ filename [ { NEW, APPEND } ] ]
Enables logging of connections in the given file. If the trailing
{ NEW, APPEND } keyword is omitted, the file is opened for appending;
i.e. new records are written to the end. If NEW is specified, a new
file is created; if a file of the same name already existed, it is
overwritten. If the filename is omitted, CX.LOG in your home (login)
directory is used (note: uppercase). To accept all defaults, just use
"log connections" (or "l c" for short). Synonym: LOG CONNECTIONS.
CLOSE CX-LOG
This closes the connection log if it was open. (Note, the CLOSE CONNECTION
command closes the connection itself).
SHOW CX
This shows your current connection, if any, including the elapsed time
(since you opened it). Synonym: SHOW CONNECTION.
v(cx_time)
This variable shows the elapsed time of your current connection, or if
there is no current connection, of your most recent connection, of if there
have been no connections, 0.
The connection contains one line per connection, of the form:
yyyymmdd hh:mm:ss username pid p=v [ p=v [ ... ] ]
where the timestamp (in columns 1-18) shows when the connection was made;
username is the login identity of the person who made the connection; pid is
Kermit's process ID when it made the connection. The p's are parameters that
depend on the type of connection, and the v's are their values:
T = Connection Type (TCP, SERIAL, DIAL, DECNET, etc).
H = The name of the Host from which the connection was made.
N = Destination phone Number or Network host name or address.
D = Serial connections only: Device name.
O = Dialed calls only: Originating country code & area code if known.
E = Elapsed time in hh:mm:ss format (or hhh:mm:ss, etc).
If you always want to keep a connection log, simply add:
log connections
to your C-Kermit customization file. Note, however, that if you make a lot of
connections, your CX.LOG will grow and grow. You can handle this by adding a
"logrotate" procedure like the following to your customization file, before
the "log connections" command:
define LOGROTATE { ; Define LOGROTATE macro
local %i %m %d %n %f MAX
def MAX 4 ; How many months to keep
if not def %1 - ; No argument given
end 1 %0: No filename given
if not = 1 ffiles(%1) - ; Exactly 1 file must match
end 1 %0: %1 - File not found
.%d := fsubstr(fdate(%1),1,6) ; Arg OK - get file year & month
if = %d - ; Compare file year & month
fsubstr(v(ndate),1,6) - ; with current year & month
end 0 ; Same year & month - done
rename %1 %1.%d ; Different - rename file
.%n := ffiles(%1.*) ; How many old files
if < %n m(MAX) end 0 ; Not enough to rotate
.%m := %1.999999 ; Initial compare string
for %i 1 %n 1 { ; Loop thru old logs
.%f := fnextfile() ; Get next file name
if llt %f %m .%m := %f ; If this one older remember it
}
delete %m ; Delete the oldest one
}
log connections ; Now open the (possibly new) log
logrotate v(home)CX.LOG ; Run the LOGROTATE macro
As you can see, this compares the yyyymm portion of the modification date
(fdate()) of the given file (%1) with the current yyyymm. If they differ,
the current file has the yyyymm suffix (from its most recent modification
date) appended to its name. Then we search through all other such files, find
the oldest one, and delete it. Thus the current log, plus the logs from the
most recent four months, are kept. This is all done automatically every time
you start C-Kermit.
On multiuser systems, it is possible to keep a single, shared, system-wide
connection log, but this is not recommended since (a) it requires you keep a
publicly write-accessible logfile (a glaring target for mischief), and (b) it
would require each user to log to that file and not disable logging. A better
method for logging connections, in UNIX at least, is syslogging (see
ckuins.txt Section 15 and iksd.txt Section 4.2 for details).
2.13. Automatic Connection-Specific Flow Control Selection
Beginning in C-Kermit 7.0, the appropriate flow-control method for each
connection type is kept in a table, for example:
Remote: NONE
Modem: RTS/CTS
Direct-Serial: NONE
TCPIP: NONE
The size of the table and values for each connection type can vary from
platform to platform. Type "set flow ?" for a list of available flow-control
types.
The table is used to automatically select the appropriate kind of flow
control whenever you make a connection. You can display the table with:
SHOW FLOW-CONTROL
The defaults are as follows:
Remote:
NONE or XON/XOFF. This is because C-Kermit is not allowed to find out what
type of connection the incoming user has (*). No kind of flow control will
work on every kind of connection, including (unexpectedly) KEEP, which we
would have liked to use, but not turning off flow control at the remote end
during file transfer on TCP/IP connections is fatal to the transfer (except
in VMS and HP-UX, where it must be set to Xon/Xoff!) Therefore if you are
dialing in to a serial port on a server (UNIX or VMS) where C-Kermit is
running, you will need to tell C-Kermit to "set flow keep" before
transferring files (assuming the modem and port are configured correctly by
the system administrator; otherwise you'll need to give a specific kind of
flow control, e.g. "set flow xon/xoff"), so in this case C-Kermit will not
disable flow control, as it must do when you are coming via Telnet (directly
or through a terminal server, except on VMS and HP-UX).
Modem:
This applies when you dial out with a modem. In this case, the MODEM
FLOW-CONTROL setting takes affect after the SET FLOW setting, so it can pick
the most appropriate flow control for the combination of the particular
modem and the computer/port/driver that is dialing.
Direct-Serial:
The default here is NONE because C-Kermit has no way of knowing what kind
of flow control, if any, is or can be done by the device at the other end
of the connection. RTS/CTS would be a bad choice here, because if the CTS
signal is not asserted, the connection will hang. And since direct
connections are often made with 3-wire cables, there is a good chance the
CTS signal will not be received.
TCPIP:
NONE, since TCP and IP provide their own flow control transparently to the
application, except in VMS, where Xon/Xoff is the default due to the
requirements of the VMS TCP/IP products.
Other networks:
NONE, since networks should provide their flow control transparently to the
application.
(*) This is possibly the worst feature of UNIX, VMS, and other platforms
where C-Kermit runs. If C-Kermit was able to ask the operating system
what kind of connection it had to the user, it could set up many things
for you automatically.
You can modify the default-flow-control table with:
SET FLOW-CONTROL /xxx { NONE, KEEP, RTS/CTS, XON/XOFF, ... }