mirror of https://github.com/mkerrisk/man-pages
116 lines
3.6 KiB
Plaintext
116 lines
3.6 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "LISTEN" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" listen
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.SH NAME
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listen \- listen for socket connections and limit the queue of incoming
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connections
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.SH SYNOPSIS
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.LP
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\fB#include <sys/socket.h>
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.br
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.sp
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int listen(int\fP \fIsocket\fP\fB, int\fP \fIbacklog\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIlisten\fP() function shall mark a connection-mode socket, specified
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by the \fIsocket\fP argument, as accepting
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connections.
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.LP
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The \fIbacklog\fP argument provides a hint to the implementation which
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the implementation shall use to limit the number of
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outstanding connections in the socket's listen queue. Implementations
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may impose a limit on \fIbacklog\fP and silently reduce the
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specified value. Normally, a larger \fIbacklog\fP argument value shall
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result in a larger or equal length of the listen queue.
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Implementations shall support values of \fIbacklog\fP up to SOMAXCONN,
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defined in \fI<sys/socket.h>\fP.
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.LP
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The implementation may include incomplete connections in its listen
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queue. The limits on the number of incomplete connections
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and completed connections queued may be different.
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.LP
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The implementation may have an upper limit on the length of the listen
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queue-either global or per accepting socket. If
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\fIbacklog\fP exceeds this limit, the length of the listen queue is
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set to the limit.
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.LP
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If \fIlisten\fP() is called with a \fIbacklog\fP argument value that
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is less than 0, the function behaves as if it had been
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called with a \fIbacklog\fP argument value of 0.
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.LP
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A \fIbacklog\fP argument of 0 may allow the socket to accept connections,
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in which case the length of the listen queue may be
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set to an implementation-defined minimum value.
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.LP
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The socket in use may require the process to have appropriate privileges
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to use the \fIlisten\fP() function.
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.SH RETURN VALUE
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.LP
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Upon successful completions, \fIlisten\fP() shall return 0; otherwise,
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-1 shall be returned and \fIerrno\fP set to indicate
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the error.
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.SH ERRORS
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.LP
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The \fIlisten\fP() function shall fail if:
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.TP 7
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.B EBADF
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The \fIsocket\fP argument is not a valid file descriptor.
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.TP 7
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.B EDESTADDRREQ
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.sp
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The socket is not bound to a local address, and the protocol does
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not support listening on an unbound socket.
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.TP 7
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.B EINVAL
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The \fIsocket\fP is already connected.
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.TP 7
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.B ENOTSOCK
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The \fIsocket\fP argument does not refer to a socket.
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.TP 7
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.B EOPNOTSUPP
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The socket protocol does not support \fIlisten\fP().
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.sp
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.LP
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The \fIlisten\fP() function may fail if:
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.TP 7
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.B EACCES
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The calling process does not have the appropriate privileges.
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.TP 7
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.B EINVAL
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The \fIsocket\fP has been shut down.
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.TP 7
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.B ENOBUFS
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Insufficient resources are available in the system to complete the
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call.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIaccept\fP() , \fIconnect\fP() , \fIsocket\fP() , the Base Definitions
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volume of IEEE\ Std\ 1003.1-2001, \fI<sys/socket.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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