BIND(2) Linux Programmer's Manual BIND(2)NAMEbind - bind a name to a socket
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
int bind(int sockfd, const struct sockaddr *my_addr, socklen_t
addrlen);
DESCRIPTIONbind() gives the socket sockfd the local address my_addr. my_addr is
addrlen bytes long. Traditionally, this is called “assigning a name to
a socket.” When a socket is created with socket(2), it exists in a
name space (address family) but has no name assigned.
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 my_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 my_addr in order to avoid compiler warnings. The following
example shows how this is done when binding a socket in the Unix
(AF_UNIX) domain:
#include <sys/socket.h>
#include <sys/un.h>
#include <stdlib.h>
#include <stdlio.h>
#define MY_SOCK_PATH "/somepath"
int
main(int argc, char *argv[])
{
int sfd;
struct sockaddr_un addr;
sfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sfd == -1) {
perror("socket");
exit(EXIT_FAILURE);
}
memset(&addr, 0, sizeof(struct sockaddr_un));
/* Clear structure */
addr.sun_family = AF_UNIX;
strncpy(addr.sun_path, MY_SOCK_PATH,
sizeof(addr.sun_path) - 1);
if (bind(sfd, (struct sockaddr *) &addr,
sizeof(struct sockaddr_un)) == -1) {
perror("bind");
exit(EXIT_FAILURE);
}
...
}
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(2).)
EADDRNOTAVAIL
A non-existent interface was requested or the requested address
was not local.
EFAULT my_addr points outside the user's accessible address space.
EINVAL The addrlen is wrong, or the socket was not in the AF_UNIX fam‐
ily.
ELOOP Too many symbolic links were encountered in resolving my_addr.
ENAMETOOLONG
my_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.
BUGS
The transparent proxy options are not described.
CONFORMING TO
SVr4, 4.4BSD (the bind() function first appeared in 4.2BSD).
NOTE
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).
SEE ALSOaccept(2), connect(2), getsockname(2), listen(2), path_resolution(2),
socket(2), getaddrinfo(3), ip(7), ipv6(7), socket(7), unix(7)Linux 2.6.7 2004-06-23 BIND(2)
