4.3BSD/usr/man/man2/listen.2

.\" Copyright (c) 1983 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)listen.2	6.2 (Berkeley) 5/14/86
.\"
.TH LISTEN 2 "May 14, 1986"
.UC 5
.SH NAME
listen \- listen for connections on a socket
.SH SYNOPSIS
.nf
.ft B
listen(s, backlog)
int s, backlog;
.fi
.SH DESCRIPTION
To accept connections, a socket
is first created with
.IR socket (2),
a willingness to accept incoming connections and
a queue limit for incoming connections are specified with
.IR listen (2),
and then the connections are
accepted with
.IR accept (2).
The
.I listen
call applies only to sockets of type
SOCK_STREAM
or
SOCK_SEQPACKET.
.PP
The
.I backlog
parameter defines the maximum length the queue of
pending connections may grow to.
If a connection
request arrives with the queue full the client may
receive an error with an indication of ECONNREFUSED,
or, if the underlying protocol supports retransmission,
the request may be ignored so that retries may succeed.
.SH "RETURN VALUE
A 0 return value indicates success; \-1 indicates an error.
.SH "ERRORS
The call fails if:
.TP 20
[EBADF]
The argument \fIs\fP is not a valid descriptor.
.TP 20
[ENOTSOCK]
The argument \fIs\fP is not a socket.
.TP 20
[EOPNOTSUPP]
The socket is not of a type that supports the operation \fIlisten\fP.
.SH "SEE ALSO"
accept(2), connect(2), socket(2)
.SH BUGS
The
.I backlog
is currently limited (silently) to 5.