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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | BUGS | EXAMPLES | SEE ALSO | COLOPHON |
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bind(2) System Calls Manual bind(2)
bind - bind a name to a socket
Standard C library (libc, -lc)
#include <sys/socket.h>
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);
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 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
EXAMPLES below.
On success, zero is returned. On error, -1 is returned, and errno
is set to indicate the error.
EACCES The address is protected, and the user is not the
superuser.
EADDRINUSE
The given address is already in use.
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
/proc/sys/net/ipv4/ip_local_port_range ip(7).
EBADF sockfd is not a valid file descriptor.
EINVAL The socket is already bound to an address.
EINVAL addrlen is wrong, or addr is not a valid address for this
socket's domain.
ENOTSOCK
The file descriptor sockfd does not refer to a socket.
EADDRNOTAVAIL
A nonexistent interface was requested or the requested
address was not local.
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).)
EFAULT addr points outside the user's accessible address space.
ELOOP Too many symbolic links were encountered in resolving addr.
ENAMETOOLONG
addr is too long.
ENOENT A component in the directory prefix of the socket pathname
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 filesystem.
Other errors may be generated by the underlying protocol modules.
POSIX.1-2008.
POSIX.1-2001, SVr4, 4.4BSD (bind() first appeared in 4.2BSD).
The transparent proxy options are not described.
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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#define MY_SOCK_PATH "/somepath"
#define LISTEN_BACKLOG 50
#define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while (0)
int
main(void)
{
int sfd, cfd;
socklen_t peer_addr_size;
struct sockaddr_un my_addr, peer_addr;
sfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sfd == -1)
handle_error("socket");
memset(&my_addr, 0, sizeof(my_addr));
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(my_addr)) == -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(peer_addr);
cfd = accept(sfd, (struct sockaddr *) &peer_addr,
&peer_addr_size);
if (cfd == -1)
handle_error("accept");
/* Code to deal with incoming connection(s)... */
if (close(sfd) == -1)
handle_error("close");
if (unlink(MY_SOCK_PATH) == -1)
handle_error("unlink");
}
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)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 bind(2)
Pages that refer to this page: accept(2), connect(2), getpeername(2), getsockname(2), io_uring_enter2(2), io_uring_enter(2), landlock_add_rule(2), listen(2), pidfd_getfd(2), seccomp_unotify(2), socket(2), socketcall(2), syscalls(2), bindresvport(3), getaddrinfo(3), getifaddrs(3), if_nameindex(3), io_uring_prep_bind(3), sctp_bindx(3), sockaddr(3type), services(5), systemd.resource-control(5), systemd.socket(5), ddp(7), inotify(7), ip(7), ipv6(7), mctp(7), netlink(7), packet(7), raw(7), sctp(7), signal-safety(7), sock_diag(7), socket(7), tcp(7), udp(7), unix(7), vsock(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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