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

       bind - bind a name to a socket

       #include <sys/types.h>	       /* See NOTES */
       #include <sys/socket.h>

       int bind(int sockfd, const struct sockaddr *addr,
		socklen_t addrlen);

       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.

       On  success,  zero is returned.	On error, -1 is returned, and errno is
       set appropriately.

       EACCES The address is protected, and the user is not the superuser.

	      The given address is already in use.

	      (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.

	      The file descriptor sockfd does not refer to a socket.

       The following errors are specific to UNIX domain (AF_UNIX) sock-

       EACCES Search permission is denied on a component  of  the  path
	      prefix.  (See also path_resolution(7).)

	      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 is too long.

       ENOENT The file does not exist.

       ENOMEM Insufficient kernel memory was available.

	      A component of the path prefix is not a directory.

       EROFS  The socket inode would reside on a read-only filesystem.

       POSIX.1-2001,  POSIX.1-2008, SVr4, 4.4BSD (bind() first appeared
       in 4.2BSD).

       POSIX.1 does not require the  inclusion	of  <sys/types.h>,  and
       this  header  file is not required on Linux.  However, some his-
       torical (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

       The transparent proxy options are not described.

       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)

       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)

	   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)

	   if (listen(sfd, LISTEN_BACKLOG) == -1)

	   /* 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,
	   if (cfd == -1)

	   /* 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) */

       accept(2),  connect(2),	getsockname(2),	 listen(2),  socket(2),
       getaddrinfo(3),	 getifaddrs(3),	 ip(7),	 ipv6(7),  path_resolu-
       tion(7), socket(7), unix(7)

       This page is  part  of  release	4.04  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				  2015-12-28			       BIND(2)