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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 appropri-
       ately.

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 family.

       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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