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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), ip(7), ipv6(7), path_resolution(7), socket(7), unix(7)

COLOPHON

       This page is part of release 3.15 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/.