socket (1)

socket [ -bcfqrvw ] [ -p command ] [ -B local address ] host port

socket [ -bcfqrvw ] [ -p command ] /path

socket [ -bcfqrvw ] [ -p command ] [ -B local address ] -s [ -l ] port

socket [ -bcfqrvw ] [ -p command ] -s [ -l ] /path

Socket creates an Internet domain TCP or a UNIX domain stream socket and connects it to stdin and stdout. The host argument can be an Internet number in dot-notation (like ``130.149.28.10'') or a domain name. In this case it must be possible to resolve the name to a valid Internet address with gethostbyname(3). The port argument can be a port number or a service name which can be mapped to a port number by getservbyname(3). If an UNIX domain socket is wanted to be created instead of an Internet socket, specify the path instead of an internet (canonical domain named or dot-notated) host. The hostname is treated as a pathname if contains at least a single slash. I.e. if one wants to create or connect to a socket in the current directory, use ./filename to specify the connection point.

-b (background)

The program forks itself into the background, detaches from its controlling tty, closes the file descriptors associated with the tty, and changes its current directory to the root directory.

-B (local address)

This option specifies which local address to binded to when making a connection.

-c (crlf)

Linefeed characters (LF) are converted to a Carriage Return Linefeed sequence (CRLF) when written to the socket. CRLF sequences read from the socket are converted to a single LF.

-f (fork)

When a server connection has been accepted, a separate process is forked to handle the connection in background.

-l (loop)

(only valid with -s) After a connection has been closed, another connection is accepted.

-p (program)

The specified command is executed for each connection. Its standard input, standard output, and standard error channels are connected to the socket. Command can be any shell command since it is passed to /bin/sh.

-q (quit)

The connection is closed when an end-of-file condition occurs on standard input.

-r (read only)

No data is read from standard input and written to the socket.

-s (server)

A server socket is created. A hostname argument is not required of Internet sockets, only the port number but a pathname is required for UNIX domain sockets.

-v (verbose)

Messages about connections etc. are issued to stderr.

-w (write only)

No data is read from the socket and written to the standard output.

-version

Socket prints its version ID and terminates. This must be the first argument to have an effect.

The command

• socket -v coma.cs.tu-berlin.de nntp

connects to the nntp port (port 119) of coma.cs.tu-berlin.de (130.149.28.10).

The command

• socket -sl 3425

creates a server socket on port 3425 on the local host and waits for a connection. After a connection has been closed, a new connection is accepted.

The command

• socket -wslqvp "echo Socket! " 1938

creates a server socket on port 1938 on the local host and waits for a connection. When a connection is accepted, the string "Socket!" is written to the socket. No data is read from the socket and written to the finger program. The connection is closed when an end-of-file condition at the standard output of the program occurs. Then a new connection is accepted.

Lots of diagnostics for failed system calls.

unknown host host

host's address could not be resolved.

Signal signal caught, exiting

Socket exits on any signal other than SIGTSTP, SIGCONT, SIGCLD, SIGQUIT.

A non-zero exit code is returned if socket terminates due to an error condition or a signal.

ip(7), tcp(7), unix(7), accept(2), bind(2), listen(2), connect(2), socket(2), gethostbyname(3), getservbyname(3)

socket -p terminates due to a SIGPIPE signal when there is more data from the socket available than the executed program wants to read.

Please report any other bugs to the author.

This manual page describes Socket-1.1.

Juergen Nickelsen <[email protected]>