.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)

.\" Portions extracted from /usr/include/sys/socket.h, which does not have

.\" any authorship information in it.  It is probably available under the GPL.

.\"

.\" %%%LICENSE_START(VERBATIM)

.\" Permission is granted to make and distribute verbatim copies of this

.\" manual provided the copyright notice and this permission notice are

.\" preserved on all copies.

.\"

.\" Permission is granted to copy and distribute modified versions of this

.\" manual under the conditions for verbatim copying, provided that the

.\" entire resulting derived work is distributed under the terms of a

.\" permission notice identical to this one.

.\"

.\" Since the Linux kernel and libraries are constantly changing, this

.\" manual page may be incorrect or out-of-date.  The author(s) assume no

.\" responsibility for errors or omissions, or for damages resulting from

.\" the use of the information contained herein.  The author(s) may not

.\" have taken the same level of care in the production of this manual,

.\" which is licensed free of charge, as they might when working

.\" professionally.

.\"

.\" Formatted or processed versions of this manual, if unaccompanied by

.\" the source, must acknowledge the copyright and authors of this work.

.\" %%%LICENSE_END

.\"

.\"

.\" Other portions are from the 6.9 (Berkeley) 3/10/91 man page:

.\"

.\" Copyright (c) 1983 The Regents of the University of California.

.\" All rights reserved.

.\"

.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)

.\" 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.

.\" %%%LICENSE_END

.\"

.\" Modified Mon Oct 21 23:05:29 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>

.\" Modified 1998 by Andi Kleen

.\" $Id: bind.2,v 1.3 1999/04/23 19:56:07 freitag Exp $

.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>

.\"

.TH BIND 2 2016-12-12 "Linux" "Linux Programmer's Manual"

.SH NAME

bind \- bind a name to a socket

.SH SYNOPSIS

.nf

.BR "#include <sys/types.h>" "          /* See NOTES */"

.B #include <sys/socket.h>

.PP

.BI "int bind(int " sockfd ", const struct sockaddr *" addr ,

.BI "         socklen_t " addrlen );

.fi

.SH DESCRIPTION

When a socket is created with

.BR socket (2),

it exists in a name space (address family) but has no address assigned to it.

.BR bind ()

assigns the address specified by

.I addr

to the socket referred to by the file descriptor

.IR sockfd .

.I addrlen

specifies the size, in bytes, of the address structure pointed to by

.IR addr .

Traditionally, this operation is called \(lqassigning a name to a socket\(rq.

.PP

It is normally necessary to assign a local address using

.BR bind ()

before a

.B SOCK_STREAM

socket may receive connections (see

.BR accept (2)).

.PP

The rules used in name binding vary between address families.

Consult the manual entries in Section 7 for detailed information.

For

.BR AF_INET ,

see

.BR ip (7);

for

.BR AF_INET6 ,

see

.BR ipv6 (7);

for

.BR AF_UNIX ,

see

.BR unix (7);

for

.BR AF_APPLETALK ,

see

.BR ddp (7);

for

.BR AF_PACKET ,

see

.BR packet (7);

for

.BR AF_X25 ,

see

.BR x25 (7);

and for

.BR AF_NETLINK ,

see

.BR netlink (7).

.PP

The actual structure passed for the

.I addr

argument will depend on the address family.

The

.I sockaddr

structure is defined as something like:

.PP

.in +4n

.EX

struct sockaddr {

    sa_family_t sa_family;

    char        sa_data[14];

}

.EE

.in

.PP

The only purpose of this structure is to cast the structure

pointer passed in

.I addr

in order to avoid compiler warnings.

See EXAMPLE below.

.SH RETURN VALUE

On success, zero is returned.

On error, \-1 is returned, and

.I errno

is set appropriately.

.SH ERRORS

.TP

.B EACCES

.\" e.g., privileged port in AF_INET domain

The address is protected, and the user is not the superuser.

.TP

.B EADDRINUSE

The given address is already in use.

.TP

.B EADDRINUSE

(Internet domain sockets)

The port number was specified as zero in the socket address structure,

but, upon attempting to bind to an ephemeral port,

it was determined that all port numbers in the ephemeral port range

are currently in use.

See the discussion of

.I /proc/sys/net/ipv4/ip_local_port_range

.BR ip (7).

.TP

.B EBADF

.I sockfd

is not a valid file descriptor.

.TP

.B EINVAL

The socket is already bound to an address.

.\" This may change in the future: see

.\" .I linux/unix/sock.c for details.

.TP

.B EINVAL

.I addrlen

is wrong, or

.I addr

is not a valid address for this socket's domain.

.TP

.B ENOTSOCK

The file descriptor

.I sockfd

does not refer to a socket.

.PP

The following errors are specific to UNIX domain

.RB ( AF_UNIX )

sockets:

.TP

.B EACCES

Search permission is denied on a component of the path prefix.

(See also

.BR path_resolution (7).)

.TP

.B EADDRNOTAVAIL

A nonexistent interface was requested or the requested

address was not local.

.TP

.B EFAULT

.I addr

points outside the user's accessible address space.

.TP

.B ELOOP

Too many symbolic links were encountered in resolving

.IR addr .

.TP

.B ENAMETOOLONG

.I addr

is too long.

.TP

.B ENOENT

A component in the directory prefix of the socket pathname does not exist.

.TP

.B ENOMEM

Insufficient kernel memory was available.

.TP

.B ENOTDIR

A component of the path prefix is not a directory.

.TP

.B EROFS

The socket inode would reside on a read-only filesystem.

.SH CONFORMING TO

POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD

.RB ( bind ()

first appeared in 4.2BSD).

.\" SVr4 documents an additional

.\" .B ENOSR

.\" general error condition, and

.\" additional

.\" .B EIO

.\" and

.\" .B EISDIR

.\" UNIX-domain error conditions.

.SH NOTES

POSIX.1 does not require the inclusion of

.IR <sys/types.h> ,

and this header file is not required on Linux.

However, some historical (BSD) implementations required this header

file, and portable applications are probably wise to include it.

.PP

For background on the

.I socklen_t

type, see

.BR accept (2).

.SH BUGS

The transparent proxy options are not described.

.\" FIXME Document transparent proxy options

.SH EXAMPLE

An example of the use of

.BR bind ()

with Internet domain sockets can be found in

.BR getaddrinfo (3).

.PP

The following example shows how to bind a stream socket in the UNIX

.RB ( AF_UNIX )

domain, and accept connections:

.\" listen.7 refers to this example.

.\" accept.7 refers to this example.

.\" unix.7 refers to this example.

.PP

.EX

#include <sys/socket.h>

#include <sys/un.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#define MY_SOCK_PATH "/somepath"

#define LISTEN_BACKLOG 50

#define handle_error(msg) \\

    do { perror(msg); exit(EXIT_FAILURE); } while (0)

int

main(int argc, char *argv[])

{

    int sfd, cfd;

    struct sockaddr_un my_addr, peer_addr;

    socklen_t peer_addr_size;

    sfd = socket(AF_UNIX, SOCK_STREAM, 0);

    if (sfd == \-1)

        handle_error("socket");

    memset(&my_addr, 0, sizeof(struct sockaddr_un));

                        /* Clear structure */

    my_addr.sun_family = AF_UNIX;

    strncpy(my_addr.sun_path, MY_SOCK_PATH,

            sizeof(my_addr.sun_path) \- 1);

    if (bind(sfd, (struct sockaddr *) &my_addr,

            sizeof(struct sockaddr_un)) == \-1)

        handle_error("bind");

    if (listen(sfd, LISTEN_BACKLOG) == \-1)

        handle_error("listen");

    /* Now we can accept incoming connections one

       at a time using accept(2) */

    peer_addr_size = sizeof(struct sockaddr_un);

    cfd = accept(sfd, (struct sockaddr *) &peer_addr,

                 &peer_addr_size);

    if (cfd == \-1)

        handle_error("accept");

    /* Code to deal with incoming connection(s)... */

    /* When no longer required, the socket pathname, MY_SOCK_PATH

       should be deleted using unlink(2) or remove(3) */

}

.EE

.SH SEE ALSO

.BR accept (2),

.BR connect (2),

.BR getsockname (2),

.BR listen (2),

.BR socket (2),

.BR getaddrinfo (3),

.BR getifaddrs (3),

.BR ip (7),

.BR ipv6 (7),

.BR path_resolution (7),

.BR socket (7),

.BR unix (7)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.