bind(2)



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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  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.

       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) sock-
       ets:

       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),
       getaddrinfo(3),  getifaddrs(3),  ip(7),  ipv6(7),   path_resolu-
       tion(7), socket(7), unix(7)

COLOPHON
       This  page  is  part  of  release  3.71  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)

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