listen(2) [mojave man page]

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 connections are specified with listen().  Finally, the connections are accepted with
     accept(2).  The listen() call applies only to sockets of type SOCK_STREAM.

     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 listening 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), connectx(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					  March 18, 2015					 4.2 Berkeley Distribution

listen(3XNET)					   X/Open Networking Services Library Functions 				     listen(3XNET)

NAME

       listen - listen for socket connections and limit the queue of incoming connections

SYNOPSIS

       cc [ flag ... ] file ... -lxnet [ library ... ]
       #include <sys/socket.h>

       int listen(int socket, int backlog);

DESCRIPTION

       The  listen() function marks a connection-mode socket, specified by the socket argument, as accepting connections, and limits the number of
       outstanding connections in the socket's listen queue to the value specified by the backlog argument.

       If listen() is called with a backlog argument value that is less than 0, the function sets the length of the socket's listen queue to 0.

       The implementation may include incomplete connections in the queue subject to the queue limit. The implementation  may  also  increase  the
       specified queue limit internally if it includes such incomplete connections in the queue subject to this limit.

       Implementations	may  limit the length of the socket's listen queue.  If backlog exceeds the implementation-dependent maximum queue length,
       the length of the socket's listen queue will be set to the maximum supported value.

       The socket in use may require the process to have appropriate privileges to use the listen() function.

RETURN VALUES

       Upon successful completions, listen() returns 0.  Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

       The listen() function will fail if:

       EBADF	       The socket argument is not a valid file descriptor.

       EDESTADDRREQ    The socket is not bound to a local address, and the protocol does not support listening on an unbound socket.

       EINVAL	       The socket is already connected.

       ENOTSOCK        The socket argument does not refer to a socket.

       EOPNOTSUPP      The socket protocol does not support listen().

       The listen() function may fail if:

       EACCES	  The calling process does not have the appropriate privileges.

       EINVAL	  The socket has been shut down.

       ENOBUFS	  Insufficient resources are available in the system to complete the call.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       accept(3XNET), connect(3XNET), socket(3XNET), attributes(5), standards(5)

SunOS 5.11							    10 Jun 2002 						     listen(3XNET)