BIND(2)



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

NAME
       bind - bind a name to a socket

SYNOPSIS
       #include <sys/types.h>
       #include <sys/socket.h>

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

DESCRIPTION
       bind() gives the socket sockfd the local address my_addr.   my_addr  is
       addrlen bytes long.  Traditionally, this is called "assigning a name to
       a socket."  When a socket is created with socket(2),  it  exists  in  a
       name space (address family) but has no name assigned.

       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 my_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 my_addr in order to avoid compiler warnings.   The  following
       example  shows  how  this  is  done  when  binding a socket in the Unix
       (AF_UNIX) domain:

         #include <sys/socket.h>
         #include <sys/un.h>
         #include <stdlib.h>
         #include <stdlio.h>

         #define MY_SOCK_PATH "/somepath"

         int
         main(int argc, char *argv[])
         {
             int sfd;
             struct sockaddr_un addr;

             sfd = socket(AF_UNIX, SOCK_STREAM, 0);
             if (sfd == -1) {
                 perror("socket");
                 exit(EXIT_FAILURE);
             }

             memset(&addr, 0, sizeof(struct sockaddr_un));
                                 /* Clear structure */
             addr.sun_family = AF_UNIX;
             strncpy(addr.sun_path, MY_SOCK_PATH,
                     sizeof(addr.sun_path) - 1);

             if (bind(sfd, (struct sockaddr *) &addr,
                     sizeof(struct sockaddr_un)) == -1) {
                 perror("bind");
                 exit(EXIT_FAILURE);
             }
             ...
         }

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(2).)

       EADDRNOTAVAIL
              A non-existent interface was requested or the requested  address
              was not local.

       EFAULT my_addr points outside the user's accessible address space.

       EINVAL The  addrlen is wrong, or the socket was not in the AF_UNIX fam-
              ily.

       ELOOP  Too many symbolic links were encountered in resolving my_addr.

       ENAMETOOLONG
              my_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.

BUGS
       The transparent proxy options are not described.

CONFORMING TO
       SVr4, 4.4BSD (the bind() function first appeared in 4.2BSD).

NOTE
       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).

SEE ALSO
       accept(2), connect(2), getsockname(2),  listen(2),  path_resolution(2),
       socket(2), getaddrinfo(3), ip(7), ipv6(7), socket(7), unix(7)

Linux 2.6.7                       2004-06-23                           BIND(2)

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