listen.2

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)listen.2	8.1	9/11/90
.TH listen 2
.SH Name
listen \- listen for connections on a socket
.SH Syntax
.nf
.ft B
listen(s, backlog)
int s, backlog;
.fi
.SH Description
.NXR "listen system call"
.NXR "listen system call" "accept system call"
.NXR "socket" "queuing connections"
To accept connections, a socket
is first created with a
.PN socket 
call, a backlog for incoming connections is specified with 
.PN listen , 
and then the connections are accepted with the
.PN accept 
call.
The
.PN listen
call is needed only for 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 
receives an error with an indication of ECONNREFUSED.
.SH Restrictions 
The 
.I backlog
is currently limited to 8.
.SH Return Values
A 0 return value indicates success.  A \-1 indicates an error.
.SH Diagnostics
The call fails under the following conditions:
.TP 15
[EBADF]
The argument \fIs\fP is not a valid descriptor.
.TP 15
[ENOTSOCK]
The argument \fIs\fP is not a socket.
.TP 15
[EOPNOTSUPP]
The socket is not of a type that supports the operation 
.PN listen .
.SH See Also
accept(2), connect(2), socket(2)