gno/usr.man/man2/listen.2

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.\"     @(#)listen.2	8.2 (Berkeley) 12/11/93
.\"
.TH LISTEN 2 "16 January 1997" GNO "System Calls"
.SH NAME
.BR listen
\- listen for connections on a socket
.SH SYNOPSIS
.br
#include <sys/socket.h>
.sp 1
int
\fBlisten\fR (int \fIs\fR, int \fIbacklog\fR);
.SH DESCRIPTION
To accept connections, a socket
is first created with
.BR socket (2),
a willingness to accept incoming connections and
a queue limit for incoming connections are specified with
.BR listen ,
and then the connections are
accepted with
.BR accept (2).
The
.BR listen 
call applies only to sockets of type
.BR SOCK_STREAM
or
.BR SOCK_SEQPACKET.
.LP
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 VALUES
A 0 return value indicates success; -1 indicates an error.
.SH ERRORS
.BR Listen 
will fail if:
.RS
.IP \fBEBADF\fR
The argument
.I s
is not a valid descriptor.
.IP \fBENOTSOCK\fR
The argument
.I s
is not a socket.
.IP \fBEOPNOTSUPP\fR
The socket is not of a type that supports the operation
.BR listen .
.RE
.SH SEE ALSO
.BR accept (2),
.BR connect (2),
.BR socket (2)
.SH BUGS
The
.I backlog
is currently limited (silently) to 32.
.SH HISTORY
The
.BR listen
function call appeared in 4.2BSD.
The first appearance in GNO was in v2.0.5.