NAME
bind - bind a name to a socket
SYNOPSIS
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);
DESCRIPTION
When a socket is created with socket(2), it exists in a name space
(address family) but has no address assigned to it. bind() assigns the
address specified to by addr to the socket referred to by the file
descriptor sockfd. addrlen specifies the size, in bytes, of the
address structure pointed to by addr. Traditionally, this operation is
called “assigning a name to a socket”.
It is normally necessary to assign a local address using bind() before
a SOCK_STREAM socket may receive connections (see accept(2)).
The rules used in name binding vary between address families. Consult
the manual entries in Section 7 for detailed information. For AF_INET
see ip(7), for AF_INET6 see ipv6(7), for AF_UNIX see unix(7), for
AF_APPLETALK see ddp(7), for AF_PACKET see packet(7), for AF_X25 see
x25(7) and for AF_NETLINK see netlink(7).
The actual structure passed for the addr argument will depend on the
address family. The sockaddr structure is defined as something like:
struct sockaddr {
sa_family_t sa_family;
char sa_data[14];
}
The only purpose of this structure is to cast the structure pointer
passed in addr in order to avoid compiler warnings. See EXAMPLE below.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
ERRORS
EACCES The address is protected, and the user is not the superuser.
EADDRINUSE
The given address is already in use.
EBADF sockfd is not a valid descriptor.
EINVAL The socket is already bound to an address.
ENOTSOCK
sockfd is a descriptor for a file, not a socket.
The following errors are specific to Unix domain (AF_UNIX) sockets:
EACCES Search permission is denied on a component of the path prefix.
(See also path_resolution(7).)
EADDRNOTAVAIL
A nonexistent interface was requested or the requested address
was not local.
EFAULT addr points outside the user’s accessible address space.
EINVAL The addrlen is wrong, or the socket was not in the AF_UNIX
family.
ELOOP Too many symbolic links were encountered in resolving addr.
ENAMETOOLONG
addr is too long.
ENOENT The file does not exist.
ENOMEM Insufficient kernel memory was available.
ENOTDIR
A component of the path prefix is not a directory.
EROFS The socket inode would reside on a read-only file system.
CONFORMING TO
SVr4, 4.4BSD, POSIX.1-2001 (bind() first appeared in 4.2BSD).
NOTES
POSIX.1-2001 does not require the inclusion of <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.
The third argument of bind() is in reality an int (and this is what 4.x
BSD and libc4 and libc5 have). Some POSIX confusion resulted in the
present socklen_t, also used by glibc. See also accept(2).
BUGS
The transparent proxy options are not described.
EXAMPLE
An example of the use of bind() with Internet domain sockets can be
found in getaddrinfo(3).
The following example shows how to bind a stream socket in the Unix
(AF_UNIX) domain, and accept connections:
#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) */
}
SEE ALSO
accept(2), connect(2), getsockname(2), listen(2), socket(2),
getaddrinfo(3), getifaddrs(3), ip(7), ipv6(7), path_resolution(7),
socket(7), unix(7)
COLOPHON
This page is part of release 3.24 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.