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LISTEN(2)                   BSD System Calls Manual                  LISTEN(2)

NAME
     listen -- listen for connections on a socket

SYNOPSIS
     #include <sys/socket.h>

     int
     listen(int socket, int backlog);

DESCRIPTION
     Creation of socket-based connections requires several operations.  First, a socket is created with
     socket(2).  Next, a willingness to accept incoming connections and a queue limit for incoming connec-tions connections
     tions are specified with listen().  Finally, the connections are accepted with accept(2).  The listen()
     call applies only to sockets of type SOCK_STREAM or SOCK_SEQPACKET.

     The backlog parameter defines the maximum length for the queue of pending connections.  If a connection
     request arrives with the queue full, the client may receive an error with an indication of
     ECONNREFUSED.  Alternatively, if the underlying protocol supports retransmission, the request may be
     ignored so that retries may succeed.

RETURN VALUES
     The listen() function returns the value 0 if successful; otherwise the value -1 is returned and the
     global variable errno is set to indicate the error.

ERRORS
     Listen() will fail if:

     [EACCES]           The current process has insufficient privileges.

     [EBADF]            The argument socket is not a valid file descriptor.

     [EDESTADDRREQ]     The socket is not bound to a local address and the protocol does not support listen-ing listening
                        ing on an unbound socket.

     [EINVAL]           socket is already connected.

     [ENOTSOCK]         The argument socket does not reference a socket.

     [EOPNOTSUPP]       The socket is not of a type that supports the operation listen().

SEE ALSO
     accept(2), connect(2), socket(2)

BUGS
     The backlog is currently limited (silently) to 128.

HISTORY
     The listen() function call appeared in 4.2BSD.

4.2 Berkeley Distribution      December 11, 1993     4.2 Berkeley Distribution