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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  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  fam‐
	      ily.

       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
       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),	getad‐
       drinfo(3),    getifaddrs(3),    ip(7),	ipv6(7),   path_resolution(7),
       socket(7), unix(7)

COLOPHON
       This page is part of release 3.54 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)
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