COMMENT(!MOD!zsh/net/tcp
Manipulation of TCP sockets
!MOD!)
The tt(zsh/net/tcp) module makes available one builtin command:

startitem()
findex(ztcp)
cindex(TCP)
cindex(sockets, TCP)
item(tt(ztcp) [ tt(-acdfltv) ] [ var(args) ])(
tt(ztcp) is implemented as a builtin to allow full use of shell
command line editing, file I/O, and job control mechanisms.

If tt(ztcp) is run with no options, it will output
the contents of its session table.
)
enditem()

subsect(Outbound Connections)
cindex(sockets, outbound TCP)

startitem()
item(tt(ztcp) [ tt(-v) ] [ tt(-d) var(fd) ] var(host) [ var(port) ])(
Open a new TCP connection to var(host).  If the var(port) is
omitted, it will default to port 23.  The connection will
be added to the session table and the shell parameter
tt(REPLY) will be set to the file descriptor associated
with that connection.

If tt(-d) is specified, the first non-option argument
will be taken as the target file descriptor for the
connection.

In order to elicit more verbose output, use tt(-v).
)
enditem()

subsect(Inbound Connections)
cindex(sockets, inbound TCP)

startitem()
item(tt(ztcp) tt(-l) [ tt(-v) ] [ tt(-d) var(fd) ] var(port))(
tt(ztcp -l) will open a socket listening on TCP
var(port).  The socket will be added to the
session table and the shell parameter tt(REPLY)
will be set to the file descriptor associated
with that listener.

If tt(-d) is specified, the first non-option argument
will be taken as the target file descriptor for
the connection.

In order to elicit more verbose output, use tt(-v).
)
item(tt(ztcp) tt(-a) [ tt(-tv) ] [ tt(-d) var(targetfd) ] var(listenfd))(
tt(ztcp -a) will accept an incoming connection
to the port associated with var(listenfd).
The connection will be added to the session
table and the shell parameter tt(REPLY) will
be set to the file descriptor associated with
the inbound connection.

If tt(-d) is specified, the first non-option argument
will be taken as the target file descriptor for the
connection.

If tt(-t) is specified, tt(ztcp) will return
if no incoming connection is pending.  Otherwise
it will wait for one.

In order to elicit more verbose output, use tt(-v).
)
enditem()

subsect(Closing Connections)
cindex(sockets, closing TCP)

startitem()
xitem(tt(ztcp) tt(-cf) [ tt(-v) ] [ var(fd) ])
item(tt(ztcp) tt(-c) [ tt(-v) ] [ var(fd) ])(
tt(ztcp -c) will close the socket associated
with var(fd).  The socket will be removed from the
session table.  If var(fd) is not specified,
tt(ztcp) will close everything in the session table.

Normally, sockets registered by zftp (see
ifzman(\
zmanref(zshmodules)
)\
ifnzman(\
noderef(The zsh/zftp Module)
)) cannot be closed this way.  In order
to force such a socket closed, use tt(-f).

In order to elicit more verbose output, use tt(-v).
)
enditem()

subsect(Example)
cindex(TCP, example)
Here is how to create a TCP connection between two instances of zsh.  We
need to pick an unassigned port; here we use the randomly chosen 5123.

On tt(host1),
example(zmodload zsh/net/tcp
ztcp -l 5123
listenfd=$REPLY
ztcp -a $listenfd
fd=$REPLY)
The second from last command blocks until there is an incoming connection.

Now create a connection from tt(host2) (which may, of course, be the same
machine):
example(zmodload zsh/net/tcp
ztcp host1 5123
fd=$REPLY)

Now on each host, tt($fd) contains a file descriptor for talking to the
other.  For example, on tt(host1):
example(print This is a message >&$fd)
and on tt(host2):
example(read -r line <&$fd; print -r - $line)
prints `tt(This is a message)'.

To tidy up, on tt(host1):
example(ztcp -c $listenfd
ztcp -c $fd)
and on tt(host2)
example(ztcp -c $fd)