The listen() function shall mark a connection-mode socket, specified by
the socket argument, as accepting connections.
The backlog argument provides a hint to the implementation which the
implementation shall use to limit the number of outstanding connections in the
socket's listen queue. Implementations may impose a limit on backlog
and silently reduce the specified value. Normally, a larger backlog
argument value shall result in a larger or equal length of the listen queue.
Implementations shall support values of backlog up to SOMAXCONN,
defined in <sys/socket.h>.
The implementation may include incomplete connections in its listen queue. The
limits on the number of incomplete connections and completed connections
queued may be different.
The implementation may have an upper limit on the length of the listen
queue-either global or per accepting socket. If backlog exceeds this
limit, the length of the listen queue is set to the limit.
If listen() is called with a backlog argument value that is less
than 0, the function behaves as if it had been called with a backlog
argument value of 0.
A backlog argument of 0 may allow the socket to accept connections, in
which case the length of the listen queue may be set to an
implementation-defined minimum value.
The socket in use may require the process to have appropriate privileges to use
the listen() function.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html