bind (2)
Leading comments
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 verbat...
NAME
bind - bind a name to a socketSYNOPSIS
#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 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 lqassigning a name to a socketrq.
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.
- 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 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.
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.
- 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 filesystem.
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (bind() first appeared in 4.2BSD).NOTES
POSIX.1 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) */ }