listen.3.man

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.TH LISTEN 3 "2004/05/16 02:35:34" "strxnet-0_9_2-4" "Linux Fast-STREAMS Sockets Library"
.SH NAME
.B listen
\- listen for socket connections and limit the queue of incoming connections
.SH SYNOPSIS
.PP
.B #include <sys/socket.h>
.HP
.BI "int listen(int " socket ", int " backlog );
.SH DESCRIPTION
.PP
The
.BR listen ()
function marks a connection-mode socket, specified by the
.I socket
argument, as accepting connections.
.PP
The
.I backlog
argument provides a hint to the implementation which the
implementation will use to limit the number of outstanding connections in the
socket's listen queue. Normally, a larger
.I backlog
argument value will result
in a larger or equal length of the listen queue.
.PP
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.
.PP
The implementation may have an upper limit on the length of the listen
queue\(emeither global or per accepting socket.  If
.I backlog
exceeds this limit, the
length of the listen queue is set to the limit.
.PP
If
.BR listen ()
is called with a
.I backlog
argument value that is less than 0, the
function behaves as if it had been called with a
.I backlog
argument value of 0.
.PP
A
.I backlog
argument of 0 may allow the
.I socket
to accept connections, in which
case the length of the listen queue may be set to an implementation-dependent
minimum value.
.PP
The
.I socket
in use may require the process to have appropriate privileges to
use the
.BR listen ()
function.
.SH CAVEATS
.PP
This system call is implemented as a
.B SIOCSOCKSYS
IOCTL.  See
.BR socksys (4)
for more information.
.SH "RETURN VALUE"
.PP
Upon successful completions,
.BR listen ()
returns 0. Otherwise, -1 is returned and
errno is set to indicate the error.
.SH ERRORS
.PP
The
.BR listen ()
function will fail if:
.TP
.RB [ EBADF ]
The
.I socket
argument is not a valid file descriptor.
.TP
.RB [ EDESTADDRREQ ]
The
.I socket
is not bound to a local address, and the protocol does not support
listening on an unbound
.IR socket .
.TP
.RB [ EINVAL ]
The
.I socket
is already connected.
.TP
.RB [ ENOTSOCK ]
The
.I socket
argument does not refer to a socket.
.TP
.RB [ EOPNOTSUPP ]
The
.I socket
protocol does not support
.BR listen ()
.PP
The
.BR listen ()
function may fail if:
.TP
.RB [ EACCES ]
The calling process does not have the appropriate privileges.
.TP
.RB [ EINVAL ]
The
.I socket
has been shut down.
.TP
.RB [ ENOBUFS ]
Insufficient resources are available in the system to complete the call.
.SH "SEE ALSO"
.PP
.BR accept (3),
.BR connect (3),
.BR socket (3),
.BR <sys/socket.h> (5).
.SH "CONFORMING TO"
.PP
The Open Group XNS Issue 5.2.
.[
xns
.]
.\"
.\"
.[
$LIST$
.]
.TI