[apple/xnu.git] / bsd / man / man2 / listen.2

.\"	$OpenBSD: listen.2,v 1.2 1996/03/19 23:15:16 niklas Exp $
.\"	$NetBSD: listen.2,v 1.7 1996/02/16 20:38:45 phil Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)listen.2	8.2 (Berkeley) 12/11/93
.\"
.Dd December 11, 1993
.Dt LISTEN 2
.Os BSD 4.2
.Sh NAME
.Nm listen
.Nd listen for connections on a socket
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Ft int
.Fo listen
.Fa "int socket"
.Fa "int backlog"
.Fc
.Sh DESCRIPTION
Creation of socket-based connections requires several operations.
First, a socket is created with
.Xr socket 2 .
Next, a willingness to accept incoming connections and
a queue limit for incoming connections are specified with
.Fn listen .
Finally, the connections are
accepted with
.Xr accept 2 .
The
.Fn listen
call applies only to sockets of type
.Dv SOCK_STREAM
or
.Dv SOCK_SEQPACKET.
.Pp
The
.Fa 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
.Er ECONNREFUSED .
Alternatively, if the underlying protocol supports retransmission,
the request may be ignored so that retries may succeed.
.Sh RETURN VALUES
.Rv -std listen
.Sh ERRORS
.Fn Listen
will fail if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EACCES
The current process has insufficient privileges.
.\" ==========
.It Bq Er EBADF
The argument
.Fa socket
is not a valid file descriptor.
.\" ==========
.It Bq Er EDESTADDRREQ
The socket is not bound to a local address
and the protocol does not support listening on an unbound socket.
.\" ==========
.It Bq Er EINVAL
.Fa socket
is already connected.
.\" ==========
.It Bq Er ENOTSOCK
The argument
.Fa socket
does not reference a socket.
.\" ==========
.It Bq Er EOPNOTSUPP
The socket is not of a type that supports the operation
.Fn listen .
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr connect 2 ,
.Xr socket 2
.Sh BUGS
The
.Fa backlog
is currently limited (silently) to 128.
.Sh HISTORY
The
.Fn listen
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	1	.\" $OpenBSD: listen.2,v 1.2 1996/03/19 23:15:16 niklas Exp $
	2	.\" $NetBSD: listen.2,v 1.7 1996/02/16 20:38:45 phil Exp $
	3	.\"
	4	.\" Copyright (c) 1983, 1991, 1993
	5	.\" The Regents of the University of California. All rights reserved.
	6	.\"
	7	.\" Redistribution and use in source and binary forms, with or without
	8	.\" modification, are permitted provided that the following conditions
	9	.\" are met:
	10	.\" 1. Redistributions of source code must retain the above copyright
	11	.\" notice, this list of conditions and the following disclaimer.
	12	.\" 2. Redistributions in binary form must reproduce the above copyright
	13	.\" notice, this list of conditions and the following disclaimer in the
	14	.\" documentation and/or other materials provided with the distribution.
	15	.\" 3. All advertising materials mentioning features or use of this software
	16	.\" must display the following acknowledgement:
	17	.\" This product includes software developed by the University of
	18	.\" California, Berkeley and its contributors.
	19	.\" 4. Neither the name of the University nor the names of its contributors
	20	.\" may be used to endorse or promote products derived from this software
	21	.\" without specific prior written permission.
	22	.\"
	23	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	24	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	25	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	26	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	27	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	28	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	29	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	30	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	31	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	32	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	33	.\" SUCH DAMAGE.
	34	.\"
	35	.\" @(#)listen.2 8.2 (Berkeley) 12/11/93
	36	.\"
	37	.Dd December 11, 1993
	38	.Dt LISTEN 2
	39	.Os BSD 4.2
	40	.Sh NAME
	41	.Nm listen
	42	.Nd listen for connections on a socket
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/socket.h>
	45	.Ft int
2d21ac55 A	46	.Fo listen
	47	.Fa "int socket"
	48	.Fa "int backlog"
	49	.Fc
9bccf70c	50	.Sh DESCRIPTION
2d21ac55 A	51	Creation of socket-based connections requires several operations.
	52	First, a socket is created with
	53	.Xr socket 2 .
	54	Next, a willingness to accept incoming connections and
9bccf70c	55	a queue limit for incoming connections are specified with
2d21ac55 A	56	.Fn listen .
2d21ac55 A	57	Finally, the connections are
9bccf70c A	58	accepted with
	59	.Xr accept 2 .
	60	The
	61	.Fn listen
	62	call applies only to sockets of type
	63	.Dv SOCK_STREAM
	64	or
	65	.Dv SOCK_SEQPACKET.
	66	.Pp
	67	The
	68	.Fa backlog
2d21ac55 A	69	parameter defines the maximum length
2d21ac55 A	70	for the queue of pending connections.
9bccf70c	71	If a connection
2d21ac55 A	72	request arrives with the queue full,
	73	the client may receive an error with an indication of
	74	.Er ECONNREFUSED .
	75	Alternatively, if the underlying protocol supports retransmission,
9bccf70c A	76	the request may be ignored so that retries may succeed.
9bccf70c A	77	.Sh RETURN VALUES
2d21ac55	78	.Rv -std listen
9bccf70c A	79	.Sh ERRORS
	80	.Fn Listen
	81	will fail if:
	82	.Bl -tag -width Er
2d21ac55 A	83	.\" ==========
	84	.It Bq Er EACCES
	85	The current process has insufficient privileges.
	86	.\" ==========
9bccf70c A	87	.It Bq Er EBADF
9bccf70c A	88	The argument
2d21ac55 A	89	.Fa socket
	90	is not a valid file descriptor.
	91	.\" ==========
	92	.It Bq Er EDESTADDRREQ
	93	The socket is not bound to a local address
	94	and the protocol does not support listening on an unbound socket.
	95	.\" ==========
	96	.It Bq Er EINVAL
	97	.Fa socket
	98	is already connected.
	99	.\" ==========
9bccf70c A	100	.It Bq Er ENOTSOCK
9bccf70c A	101	The argument
2d21ac55 A	102	.Fa socket
	103	does not reference a socket.
	104	.\" ==========
9bccf70c A	105	.It Bq Er EOPNOTSUPP
	106	The socket is not of a type that supports the operation
	107	.Fn listen .
	108	.El
	109	.Sh SEE ALSO
	110	.Xr accept 2 ,
	111	.Xr connect 2 ,
	112	.Xr socket 2
	113	.Sh BUGS
	114	The
	115	.Fa backlog
	116	is currently limited (silently) to 128.
	117	.Sh HISTORY
	118	The
	119	.Fn listen
	120	function call appeared in
	121	.Bx 4.2 .