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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 (ad-
       dress family) but has no	address	assigned to it.	  bind()  assigns  the
       address	specified  by  addr  to	the socket referred to by the file de-
       scriptor	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.

       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 discus-
	      sion 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
	      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.

       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 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2014-08-19			       BIND(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | BUGS | EXAMPLE | SEE ALSO | COLOPHON

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