BIND(2) 						     Linux Programmer's Manual							   BIND(2)

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 3.25 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/.

Linux								    2007-12-28								   BIND(2)