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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),   getifaddrs(3),  ip(7),  ipv6(7),  path_resolution(7),
       socket(7), unix(7)

COLOPHON

       This page is part of release 3.27 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/.