bind(2) - Linux manual page (original) (raw)
bind(2) System Calls Manual bind(2)
NAME top
bind - bind a name to a socketLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/socket.h>**
**int bind(int** _sockfd_**, const struct sockaddr ***_addr_**,**
**socklen_t** _addrlen_**);**DESCRIPTION top
When a socket is created with [socket(2)](../man2/socket.2.html), 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)](../man2/accept.2.html)).
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)](../man7/ip.7.html); for **AF_INET6**, see [ipv6(7)](../man7/ipv6.7.html); for **AF_UNIX**,
see [unix(7)](../man7/unix.7.html); for **AF_APPLETALK**, see [ddp(7)](../man7/ddp.7.html); for **AF_PACKET**, see
[packet(7)](../man7/packet.7.html); for **AF_X25**, see [x25(7)](../man7/x25.7.html); and for **AF_NETLINK**, see
[netlink(7)](../man7/netlink.7.html).
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.RETURN VALUE top
On success, zero is returned. On error, -1 is returned, and _[errno](../man3/errno.3.html)_
is set to indicate the error.ERRORS top
**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/iplocalportrange_ [ip(7)](../man7/ip.7.html).
**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)](../man7/path%5Fresolution.7.html).)
**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.STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001, SVr4, 4.4BSD (**bind**() first appeared in 4.2BSD).BUGS top
The transparent proxy options are not described.EXAMPLES top
An example of the use of **bind**() with Internet domain sockets can
be found in [getaddrinfo(3)](../man3/getaddrinfo.3.html).
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");
}SEE ALSO top
[accept(2)](../man2/accept.2.html), [connect(2)](../man2/connect.2.html), [getsockname(2)](../man2/getsockname.2.html), [listen(2)](../man2/listen.2.html), [socket(2)](../man2/socket.2.html),
[getaddrinfo(3)](../man3/getaddrinfo.3.html), [getifaddrs(3)](../man3/getifaddrs.3.html), [ip(7)](../man7/ip.7.html), [ipv6(7)](../man7/ipv6.7.html), [path_resolution(7)](../man7/path%5Fresolution.7.html),
[socket(7)](../man7/socket.7.html), [unix(7)](../man7/unix.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-11-06 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), netlink(7), packet(7), raw(7), sctp(7), signal-safety(7), sock_diag(7), socket(7), tcp(7), udp(7), unix(7), vsock(7)