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listen(3) [linux man page]

LISTEN(P)						     POSIX Programmer's Manual							 LISTEN(P)

NAME
listen - listen for socket connections and limit the queue of incoming connections SYNOPSIS
#include <sys/socket.h> int listen(int socket, int backlog); DESCRIPTION
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 connec- tions 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 back- log 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 argu- ment 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 implemen- tation-defined minimum value. The socket in use may require the process to have appropriate privileges to use the listen() function. RETURN VALUE
Upon successful completions, listen() shall return 0; otherwise, -1 shall be returned and errno set to indicate the error. ERRORS
The listen() function shall 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. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
None. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
accept() , connect() , socket() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- 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 . IEEE
/The Open Group 2003 LISTEN(P)

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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 5.10 10 Jun 2002 listen(3XNET)

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