Provided by: zsh-common_5.8.1-1_all 
NAME
zshtcpsys - zsh tcp system
DESCRIPTION
A module zsh/net/tcp is provided to provide network I/O over TCP/IP from within the shell;
see its description in zshmodules(1). This manual page describes a function suite based
on the module. If the module is installed, the functions are usually installed at the
same time, in which case they will be available for autoloading in the default function
search path. In addition to the zsh/net/tcp module, the zsh/zselect module is used to
implement timeouts on read operations. For troubleshooting tips, consult the
corresponding advice for the zftp functions described in zshzftpsys(1).
There are functions corresponding to the basic I/O operations open, close, read and send,
named tcp_open etc., as well as a function tcp_expect for pattern match analysis of data
read as input. The system makes it easy to receive data from and send data to multiple
named sessions at once. In addition, it can be linked with the shell's line editor in
such a way that input data is automatically shown at the terminal. Other facilities
available including logging, filtering and configurable output prompts.
To use the system where it is available, it should be enough to `autoload -U tcp_open' and
run tcp_open as documented below to start a session. The tcp_open function will autoload
the remaining functions.
TCP USER FUNCTIONS
Basic I/O
tcp_open [ -qz ] host port [ sess ]
tcp_open [ -qz ] [ -s sess | -l sess[,...] ] ...
tcp_open [ -qz ] [ -a fd | -f fd ] [ sess ]
Open a new session. In the first and simplest form, open a TCP connection to host
host at port port; numeric and symbolic forms are understood for both.
If sess is given, this becomes the name of the session which can be used to refer
to multiple different TCP connections. If sess is not given, the function will
invent a numeric name value (note this is not the same as the file descriptor to
which the session is attached). It is recommended that session names not include
`funny' characters, where funny characters are not well-defined but certainly do
not include alphanumerics or underscores, and certainly do include whitespace.
In the second case, one or more sessions to be opened are given by name. A single
session name is given after -s and a comma-separated list after -l; both options
may be repeated as many times as necessary. A failure to open any session causes
tcp_open to abort. The host and port are read from the file .ztcp_sessions in the
same directory as the user's zsh initialisation files, i.e. usually the home
directory, but $ZDOTDIR if that is set. The file consists of lines each giving a
session name and the corresponding host and port, in that order (note the session
name comes first, not last), separated by whitespace.
The third form allows passive and fake TCP connections. If the option -a is used,
its argument is a file descriptor open for listening for connections. No function
front-end is provided to open such a file descriptor, but a call to `ztcp -l port'
will create one with the file descriptor stored in the parameter $REPLY. The
listening port can be closed with `ztcp -c fd'. A call to `tcp_open -a fd' will
block until a remote TCP connection is made to port on the local machine. At this
point, a session is created in the usual way and is largely indistinguishable from
an active connection created with one of the first two forms.
If the option -f is used, its argument is a file descriptor which is used directly
as if it were a TCP session. How well the remainder of the TCP function system
copes with this depends on what actually underlies this file descriptor. A regular
file is likely to be unusable; a FIFO (pipe) of some sort will work better, but
note that it is not a good idea for two different sessions to attempt to read from
the same FIFO at once.
If the option -q is given with any of the three forms, tcp_open will not print
informational messages, although it will in any case exit with an appropriate
status.
If the line editor (zle) is in use, which is typically the case if the shell is
interactive, tcp_open installs a handler inside zle which will check for new data
at the same time as it checks for keyboard input. This is convenient as the shell
consumes no CPU time while waiting; the test is performed by the operating system.
Giving the option -z to any of the forms of tcp_open prevents the handler from
being installed, so data must be read explicitly. Note, however, this is not
necessary for executing complete sets of send and read commands from a function, as
zle is not active at this point. Generally speaking, the handler is only active
when the shell is waiting for input at a command prompt or in the vared builtin.
The option has no effect if zle is not active; `[[ -o zle]]' will test for this.
The first session to be opened becomes the current session and subsequent calls to
tcp_open do not change it. The current session is stored in the parameter
$TCP_SESS; see below for more detail about the parameters used by the system.
The function tcp_on_open, if defined, is called when a session is opened. See the
description below.
tcp_close [ -qn ] [ -a | -l sess[,...] | sess ... ]
Close the named sessions, or the current session if none is given, or all open
sessions if -a is given. The options -l and -s are both handled for consistency
with tcp_open, although the latter is redundant.
If the session being closed is the current one, $TCP_SESS is unset, leaving no
current session, even if there are other sessions still open.
If the session was opened with tcp_open -f, the file descriptor is closed so long
as it is in the range 0 to 9 accessible directly from the command line. If the
option -n is given, no attempt will be made to close file descriptors in this case.
The -n option is not used for genuine ztcp session; the file descriptors are always
closed with the session.
If the option -q is given, no informational messages will be printed.
tcp_read [ -bdq ] [ -t TO ] [ -T TO ]
[ -a | -u fd[,...] | -l sess[,...] | -s sess ... ]
Perform a read operation on the current session, or on a list of sessions if any
are given with -u, -l or -s, or all open sessions if the option -a is given. Any
of the -u, -l or -s options may be repeated or mixed together. The -u option
specifies a file descriptor directly (only those managed by this system are
useful), the other two specify sessions as described for tcp_open above.
The function checks for new data available on all the sessions listed. Unless the
-b option is given, it will not block waiting for new data. Any one line of data
from any of the available sessions will be read, stored in the parameter $TCP_LINE,
and displayed to standard output unless $TCP_SILENT contains a non-empty string.
When printed to standard output the string $TCP_PROMPT will be shown at the start
of the line; the default form for this includes the name of the session being read.
See below for more information on these parameters. In this mode, tcp_read can be
called repeatedly until it returns status 2 which indicates all pending input from
all specified sessions has been handled.
With the option -b, equivalent to an infinite timeout, the function will block
until a line is available to read from one of the specified sessions. However,
only a single line is returned.
The option -d indicates that all pending input should be drained. In this case
tcp_read may process multiple lines in the manner given above; only the last is
stored in $TCP_LINE, but the complete set is stored in the array $tcp_lines. This
is cleared at the start of each call to tcp_read.
The options -t and -T specify a timeout in seconds, which may be a floating point
number for increased accuracy. With -t the timeout is applied before each line
read. With -T, the timeout applies to the overall operation, possibly including
multiple read operations if the option -d is present; without this option, there is
no distinction between -t and -T.
The function does not print informational messages, but if the option -q is given,
no error message is printed for a non-existent session.
A return status of 2 indicates a timeout or no data to read. Any other non-zero
return status indicates some error condition.
See tcp_log for how to control where data is sent by tcp_read.
tcp_send [ -cnq ] [ -s sess | -l sess[,...] ] data ...
tcp_send [ -cnq ] -a data ...
Send the supplied data strings to all the specified sessions in turn. The
underlying operation differs little from a `print -r' to the session's file
descriptor, although it attempts to prevent the shell from dying owing to a SIGPIPE
caused by an attempt to write to a defunct session.
The option -c causes tcp_send to behave like cat. It reads lines from standard
input until end of input and sends them in turn to the specified session(s) exactly
as if they were given as data arguments to individual tcp_send commands.
The option -n prevents tcp_send from putting a newline at the end of the data
strings.
The remaining options all behave as for tcp_read.
The data arguments are not further processed once they have been passed to
tcp_send; they are simply passed down to print -r.
If the parameter $TCP_OUTPUT is a non-empty string and logging is enabled then the
data sent to each session will be echoed to the log file(s) with $TCP_OUTPUT in
front where appropriate, much in the manner of $TCP_PROMPT.
Session Management
tcp_alias [ -q ] alias=sess ...
tcp_alias [ -q ] [ alias ... ]
tcp_alias -d [ -q ] alias ...
This function is not particularly well tested.
The first form creates an alias for a session name; alias can then be used to refer
to the existing session sess. As many aliases may be listed as required.
The second form lists any aliases specified, or all aliases if none.
The third form deletes all the aliases listed. The underlying sessions are not
affected.
The option -q suppresses an inconsistently chosen subset of error messages.
tcp_log [ -asc ] [ -n | -N ] [ logfile ]
With an argument logfile, all future input from tcp_read will be logged to the
named file. Unless -a (append) is given, this file will first be truncated or
created empty. With no arguments, show the current status of logging.
With the option -s, per-session logging is enabled. Input from tcp_read is output
to the file logfile.sess. As the session is automatically discriminated by the
filename, the contents are raw (no $TCP_PROMPT). The option -a applies as above.
Per-session logging and logging of all data in one file are not mutually exclusive.
The option -c closes all logging, both complete and per-session logs.
The options -n and -N respectively turn off or restore output of data read by
tcp_read to standard output; hence `tcp_log -cn' turns off all output by tcp_read.
The function is purely a convenient front end to setting the parameters $TCP_LOG,
$TCP_LOG_SESS, $TCP_SILENT, which are described below.
tcp_rename old new
Rename session old to session new. The old name becomes invalid.
tcp_sess [ sess [ command [ arg ... ] ] ]
With no arguments, list all the open sessions and associated file descriptors. The
current session is marked with a star. For use in functions, direct access to the
parameters $tcp_by_name, $tcp_by_fd and $TCP_SESS is probably more convenient; see
below.
With a sess argument, set the current session to sess. This is equivalent to
changing $TCP_SESS directly.
With additional arguments, temporarily set the current session while executing
`command arg ...'. command is re-evaluated so as to expand aliases etc., but the
remaining args are passed through as that appear to tcp_sess. The original session
is restored when tcp_sess exits.
Advanced I/O
tcp_command send-option ... send-argument ...
This is a convenient front-end to tcp_send. All arguments are passed to tcp_send,
then the function pauses waiting for data. While data is arriving at least every
$TCP_TIMEOUT (default 0.3) seconds, data is handled and printed out according to
the current settings. Status 0 is always returned.
This is generally only useful for interactive use, to prevent the display becoming
fragmented by output returned from the connection. Within a programme or function
it is generally better to handle reading data by a more explicit method.
tcp_expect [ -q ] [ -p var | -P var ] [ -t TO | -T TO ]
[ -a | -s sess | -l sess[,...] ] pattern ...
Wait for input matching any of the given patterns from any of the specified
sessions. Input is ignored until an input line matches one of the given patterns;
at this point status zero is returned, the matching line is stored in $TCP_LINE,
and the full set of lines read during the call to tcp_expect is stored in the array
$tcp_expect_lines.
Sessions are specified in the same way as tcp_read: the default is to use the
current session, otherwise the sessions specified by -a, -s, or -l are used.
Each pattern is a standard zsh extended-globbing pattern; note that it needs to be
quoted to avoid it being expanded immediately by filename generation. It must
match the full line, so to match a substring there must be a `*' at the start and
end. The line matched against includes the $TCP_PROMPT added by tcp_read. It is
possible to include the globbing flags `#b' or `#m' in the patterns to make
backreferences available in the parameters $MATCH, $match, etc., as described in
the base zsh documentation on pattern matching.
Unlike tcp_read, the default behaviour of tcp_expect is to block indefinitely until
the required input is found. This can be modified by specifying a timeout with -t
or -T; these function as in tcp_read, specifying a per-read or overall timeout,
respectively, in seconds, as an integer or floating-point number. As tcp_read, the
function returns status 2 if a timeout occurs.
The function returns as soon as any one of the patterns given match. If the caller
needs to know which of the patterns matched, the option -p var can be used; on
return, $var is set to the number of the pattern using ordinary zsh indexing, i.e.
the first is 1, and so on. Note the absence of a `$' in front of var. To avoid
clashes, the parameter cannot begin with `_expect'. The index -1 is used if there
is a timeout and 0 if there is no match.
The option -P var works similarly to -p, but instead of numerical indexes the
regular arguments must begin with a prefix followed by a colon: that prefix is then
used as a tag to which var is set when the argument matches. The tag timeout is
used if there is a timeout and the empty string if there is no match. Note it is
acceptable for different arguments to start with the same prefix if the matches do
not need to be distinguished.
The option -q is passed directly down to tcp_read.
As all input is done via tcp_read, all the usual rules about output of lines read
apply. One exception is that the parameter $tcp_lines will only reflect the line
actually matched by tcp_expect; use $tcp_expect_lines for the full set of lines
read during the function call.
tcp_proxy
This is a simple-minded function to accept a TCP connection and execute a command
with I/O redirected to the connection. Extreme caution should be taken as there is
no security whatsoever and this can leave your computer open to the world.
Ideally, it should only be used behind a firewall.
The first argument is a TCP port on which the function will listen.
The remaining arguments give a command and its arguments to execute with standard
input, standard output and standard error redirected to the file descriptor on
which the TCP session has been accepted. If no command is given, a new zsh is
started. This gives everyone on your network direct access to your account, which
in many cases will be a bad thing.
The command is run in the background, so tcp_proxy can then accept new connections.
It continues to accept new connections until interrupted.
tcp_spam [ -ertv ] [ -a | -s sess | -l sess[,...] ] cmd [ arg ... ]
Execute `cmd [ arg ... ]' for each session in turn. Note this executes the command
and arguments; it does not send the command line as data unless the -t (transmit)
option is given.
The sessions may be selected explicitly with the standard -a, -s or -l options, or
may be chosen implicitly. If none of the three options is given the rules are:
first, if the array $tcp_spam_list is set, this is taken as the list of sessions,
otherwise all sessions are taken. Second, any sessions given in the array
$tcp_no_spam_list are removed from the list of sessions.
Normally, any sessions added by the `-a' flag or when all sessions are chosen
implicitly are spammed in alphabetic order; sessions given by the $tcp_spam_list
array or on the command line are spammed in the order given. The -r flag reverses
the order however it was arrived it.
The -v flag specifies that a $TCP_PROMPT will be output before each session. This
is output after any modification to TCP_SESS by the user-defined tcp_on_spam
function described below. (Obviously that function is able to generate its own
output.)
If the option -e is present, the line given as `cmd [ arg ... ]' is executed using
eval, otherwise it is executed without any further processing.
tcp_talk
This is a fairly simple-minded attempt to force input to the line editor to go
straight to the default TCP_SESS.
An escape string, $TCP_TALK_ESCAPE, default `:', is used to allow access to normal
shell operation. If it is on its own at the start of the line, or followed only by
whitespace, the line editor returns to normal operation. Otherwise, the string and
any following whitespace are skipped and the remainder of the line executed as
shell input without any change of the line editor's operating mode.
The current implementation is somewhat deficient in terms of use of the command
history. For this reason, many users will prefer to use some form of alternative
approach for sending data easily to the current session. One simple approach is to
alias some special character (such as `%') to `tcp_command --'.
tcp_wait
The sole argument is an integer or floating point number which gives the seconds to
delay. The shell will do nothing for that period except wait for input on all TCP
sessions by calling tcp_read -a. This is similar to the interactive behaviour at
the command prompt when zle handlers are installed.
`One-shot' file transfer
tcp_point port
tcp_shoot host port
This pair of functions provide a simple way to transfer a file between two hosts
within the shell. Note, however, that bulk data transfer is currently done using
cat. tcp_point reads any data arriving at port and sends it to standard output;
tcp_shoot connects to port on host and sends its standard input. Any unused port
may be used; the standard mechanism for picking a port is to think of a random
four-digit number above 1024 until one works.
To transfer a file from host woodcock to host springes, on springes:
tcp_point 8091 >output_file
and on woodcock:
tcp_shoot springes 8091 <input_file
As these two functions do not require tcp_open to set up a TCP connection first,
they may need to be autoloaded separately.
TCP USER-DEFINED FUNCTIONS
Certain functions, if defined by the user, will be called by the function system in
certain contexts. This facility depends on the module zsh/parameter, which is usually
available in interactive shells as the completion system depends on it. None of the
functions need be defined; they simply provide convenient hooks when necessary.
Typically, these are called after the requested action has been taken, so that the various
parameters will reflect the new state.
tcp_on_alias alias fd
When an alias is defined, this function will be called with two arguments: the name
of the alias, and the file descriptor of the corresponding session.
tcp_on_awol sess fd
If the function tcp_fd_handler is handling input from the line editor and detects
that the file descriptor is no longer reusable, by default it removes it from the
list of file descriptors handled by this method and prints a message. If the
function tcp_on_awol is defined it is called immediately before this point. It may
return status 100, which indicates that the normal handling should still be
performed; any other return status indicates that no further action should be taken
and the tcp_fd_handler should return immediately with the given status. Typically
the action of tcp_on_awol will be to close the session.
The variable TCP_INVALIDATE_ZLE will be a non-empty string if it is necessary to
invalidate the line editor display using `zle -I' before printing output from the
function.
(`AWOL' is military jargon for `absent without leave' or some variation. It has no
pre-existing technical meaning known to the author.)
tcp_on_close sess fd
This is called with the name of a session being closed and the file descriptor
which corresponded to that session. Both will be invalid by the time the function
is called.
tcp_on_open sess fd
This is called after a new session has been defined with the session name and file
descriptor as arguments. If it returns a non-zero status, opening the session is
assumed to fail and the session is closed again; however, tcp_open will continue to
attempt to open any remaining sessions given on the command line.
tcp_on_rename oldsess fd newsess
This is called after a session has been renamed with the three arguments old
session name, file descriptor, new session name.
tcp_on_spam sess command ...
This is called once for each session spammed, just before a command is executed for
a session by tcp_spam. The arguments are the session name followed by the command
list to be executed. If tcp_spam was called with the option -t, the first command
will be tcp_send.
This function is called after $TCP_SESS is set to reflect the session to be
spammed, but before any use of it is made. Hence it is possible to alter the value
of $TCP_SESS within this function. For example, the session arguments to tcp_spam
could include extra information to be stripped off and processed in tcp_on_spam.
If the function sets the parameter $REPLY to `done', the command line is not
executed; in addition, no prompt is printed for the -v option to tcp_spam.
tcp_on_unalias alias fd
This is called with the name of an alias and the corresponding session's file
descriptor after an alias has been deleted.
TCP UTILITY FUNCTIONS
The following functions are used by the TCP function system but will rarely if ever need
to be called directly.
tcp_fd_handler
This is the function installed by tcp_open for handling input from within the line
editor, if that is required. It is in the format documented for the builtin `zle
-F' in zshzle(1) .
While active, the function sets the parameter TCP_HANDLER_ACTIVE to 1. This allows
shell code called internally (for example, by setting tcp_on_read) to tell if is
being called when the shell is otherwise idle at the editor prompt.
tcp_output [ -q ] -P prompt -F fd -S sess
This function is used for both logging and handling output to standard output, from
within tcp_read and (if $TCP_OUTPUT is set) tcp_send.
The prompt to use is specified by -P; the default is the empty string. It can
contain:
%c Expands to 1 if the session is the current session, otherwise 0. Used with
ternary expressions such as `%(c.-.+)' to output `+' for the current session
and `-' otherwise.
%f Replaced by the session's file descriptor.
%s Replaced by the session name.
%% Replaced by a single `%'.
The option -q suppresses output to standard output, but not to any log files which
are configured.
The -S and -F options are used to pass in the session name and file descriptor for
possible replacement in the prompt.
TCP USER PARAMETERS
Parameters follow the usual convention that uppercase is used for scalars and integers,
while lowercase is used for normal and associative array. It is always safe for user code
to read these parameters. Some parameters may also be set; these are noted explicitly.
Others are included in this group as they are set by the function system for the user's
benefit, i.e. setting them is typically not useful but is benign.
It is often also useful to make settable parameters local to a function. For example,
`local TCP_SILENT=1' specifies that data read during the function call will not be printed
to standard output, regardless of the setting outside the function. Likewise, `local
TCP_SESS=sess' sets a session for the duration of a function, and `local TCP_PROMPT='
specifies that no prompt is used for input during the function.
tcp_expect_lines
Array. The set of lines read during the last call to tcp_expect, including the
last ($TCP_LINE).
tcp_filter
Array. May be set directly. A set of extended globbing patterns which, if matched
in tcp_output, will cause the line not to be printed to standard output. The
patterns should be defined as described for the arguments to tcp_expect. Output of
line to log files is not affected.
TCP_HANDLER_ACTIVE
Scalar. Set to 1 within tcp_fd_handler to indicate to functions called recursively
that they have been called during an editor session. Otherwise unset.
TCP_LINE
The last line read by tcp_read, and hence also tcp_expect.
TCP_LINE_FD
The file descriptor from which $TCP_LINE was read. ${tcp_by_fd[$TCP_LINE_FD]} will
give the corresponding session name.
tcp_lines
Array. The set of lines read during the last call to tcp_read, including the last
($TCP_LINE).
TCP_LOG
May be set directly, although it is also controlled by tcp_log. The name of a file
to which output from all sessions will be sent. The output is proceeded by the
usual $TCP_PROMPT. If it is not an absolute path name, it will follow the user's
current directory.
TCP_LOG_SESS
May be set directly, although it is also controlled by tcp_log. The prefix for a
set of files to which output from each session separately will be sent; the full
filename is ${TCP_LOG_SESS}.sess. Output to each file is raw; no prompt is added.
If it is not an absolute path name, it will follow the user's current directory.
tcp_no_spam_list
Array. May be set directly. See tcp_spam for how this is used.
TCP_OUTPUT
May be set directly. If a non-empty string, any data sent to a session by tcp_send
will be logged. This parameter gives the prompt to be used in a file specified by
$TCP_LOG but not in a file generated from $TCP_LOG_SESS. The prompt string has the
same format as TCP_PROMPT and the same rules for its use apply.
TCP_PROMPT
May be set directly. Used as the prefix for data read by tcp_read which is printed
to standard output or to the log file given by $TCP_LOG, if any. Any `%s', `%f' or
`%%' occurring in the string will be replaced by the name of the session, the
session's underlying file descriptor, or a single `%', respectively. The
expression `%c' expands to 1 if the session being read is the current session, else
0; this is most useful in ternary expressions such as `%(c.-.+)' which outputs `+'
if the session is the current one, else `-'.
If the prompt starts with %P, this is stripped and the complete result of the
previous stage is passed through standard prompt %-style formatting before being
output.
TCP_READ_DEBUG
May be set directly. If this has non-zero length, tcp_read will give some limited
diagnostics about data being read.
TCP_SECONDS_START
This value is created and initialised to zero by tcp_open.
The functions tcp_read and tcp_expect use the shell's SECONDS parameter for their
own timing purposes. If that parameter is not of floating point type on entry to
one of the functions, it will create a local parameter SECONDS which is floating
point and set the parameter TCP_SECONDS_START to the previous value of $SECONDS.
If the parameter is already floating point, it is used without a local copy being
created and TCP_SECONDS_START is not set. As the global value is zero, the shell
elapsed time is guaranteed to be the sum of $SECONDS and $TCP_SECONDS_START.
This can be avoided by setting SECONDS globally to a floating point value using
`typeset -F SECONDS'; then the TCP functions will never make a local copy and never
set TCP_SECONDS_START to a non-zero value.
TCP_SESS
May be set directly. The current session; must refer to one of the sessions
established by tcp_open.
TCP_SILENT
May be set directly, although it is also controlled by tcp_log. If of non-zero
length, data read by tcp_read will not be written to standard output, though may
still be written to a log file.
tcp_spam_list
Array. May be set directly. See the description of the function tcp_spam for how
this is used.
TCP_TALK_ESCAPE
May be set directly. See the description of the function tcp_talk for how this is
used.
TCP_TIMEOUT
May be set directly. Currently this is only used by the function tcp_command, see
above.
TCP USER-DEFINED PARAMETERS
The following parameters are not set by the function system, but have a special effect if
set by the user.
tcp_on_read
This should be an associative array; if it is not, the behaviour is undefined.
Each key is the name of a shell function or other command, and the corresponding
value is a shell pattern (using EXTENDED_GLOB). Every line read from a TCP session
directly or indirectly using tcp_read (which includes lines read by tcp_expect) is
compared against the pattern. If the line matches, the command given in the key is
called with two arguments: the name of the session from which the line was read,
and the line itself.
If any function called to handle a line returns a non-zero status, the line is not
output. Thus a tcp_on_read handler containing only the instruction `return 1' can
be used to suppress output of particular lines (see, however, tcp_filter above).
However, the line is still stored in TCP_LINE and tcp_lines; this occurs after all
tcp_on_read processing.
TCP UTILITY PARAMETERS
These parameters are controlled by the function system; they may be read directly, but
should not usually be set by user code.
tcp_aliases
Associative array. The keys are the names of sessions established with tcp_open;
each value is a space-separated list of aliases which refer to that session.
tcp_by_fd
Associative array. The keys are session file descriptors; each value is the name
of that session.
tcp_by_name
Associative array. The keys are the names of sessions; each value is the file
descriptor associated with that session.
TCP EXAMPLES
Here is a trivial example using a remote calculator.
To create a calculator server on port 7337 (see the dc manual page for quite how
infuriating the underlying command is):
tcp_proxy 7337 dc
To connect to this from the same host with a session also named `dc':
tcp_open localhost 7337 dc
To send a command to the remote session and wait a short while for output (assuming dc is
the current session):
tcp_command 2 4 + p
To close the session:
tcp_close
The tcp_proxy needs to be killed to be stopped. Note this will not usually kill any
connections which have already been accepted, and also that the port is not immediately
available for reuse.
The following chunk of code puts a list of sessions into an xterm header, with the current
session followed by a star.
print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"
TCP BUGS
The function tcp_read uses the shell's normal read builtin. As this reads a complete line
at once, data arriving without a terminating newline can cause the function to block
indefinitely.
Though the function suite works well for interactive use and for data arriving in small
amounts, the performance when large amounts of data are being exchanged is likely to be
extremely poor.