BIND

C Interface

   AF_UNIX only:



        #include <sys/types.h>

        #include <sys/socket.h>

        #include <sys/un.h>



        bind(s, addr, addrlen)

        int s;

        struct sockaddr_un *addr;

        int addrlen;



   AF_INET only:



        #include <sys/types.h>

        #include <sys/socket.h>

        #include <netinet/in.h>



        bind(s, addr, addrlen)

        int s;

        struct sockaddr_in *addr;

        int addrlen;

Description

The bind system call assigns an address to an unbound socket. When a socket is created with socket, it exists in an address space (address family) but has no address assigned. The bind call causes the socket whose descriptor is s to become bound to the address specified in the socket address structure pointed to by addr. The addrlen parameter must specify the size of the address structure. Since the size of the socket address structure varies between socket address families (16 bytes for AF_INET; 110 bytes for AF_UNIX), the correct socket address structure should be used with each address family (struct sockaddr_in for AF_INET; struct sockaddr_un for AF_UNIX).

Here is the socket address structure for AF_INET, extracted from the IN.H.SYS file:

   struct in_addr {

       union {

           struct { u_char s_b1,s_b2,s_b3,s_b4; } s_un_b;

           struct { u_short s_w1,s_w2; } S_un_w;

           u_long S_addr;

       } S_un;

   #define s_addr  S_un.S_addr /* can be used for most tcp & ip code 

   */

   #define s_host  S_un.S_un_b.s_b2     /* host on imp  */

   #define s_net   S_un.S_un_b.s_b1     /* network      */

   #define s_imp   S_un.S_un_w.s_w2     /* imp          */

   #define s_impno S_un.S_un_b.s_b4     /* imp #        */

   #define s_lh    S_un.S_un_b.s_b3     /* logical host */

   };



   #define      INADDR_ANY        (u_long)0x00000000

   #define      INADDR_THISHOST   (u_long)0x00000000



   struct sockaddr_in {

       short    sin_family;

       u_short  sin_port;

       struct   in_addr sin_addr;

       char     sin_zero[8];

   };

Here is the socket address structure for AF_UNIX, extracted from the UN.H.SYS file:

   struct  sockaddr_un {

           short   sun_family;         /* AF_UNIX         */

           char    sun_path[108];      /* path name       */

   };

Examples

Here is an example program to create and bind an AF_UNIX socket:

   #include <sys/types.h>

   #include <sys/socket.h>

   #include <sys/errno.h>

   #include <sys/un.h>



   main ()

   {

   int s;

   int af, type, protocol;

   struct sockaddr_un addr;

   int addrlen;



   s = socket (AF_UNIX, SOCK_STREAM, 0);



   addr.sun_family = AF_UNIX;

   strcpy (addr.sun_path,"tmp/socket");

   addrlen = 110;



   bind (s,addr, addrlen);



   }

Return Value

If the bind is successful, a 0 value is returned. If it fails, -1 is returned, and an error code is stored in errno.

Errors

The following errors are returned by bind:

[EBADF]: The argument s is not a valid descriptor.
[ENOTSOCK]: The argument s is not a socket.
[EADDRNOTAVAIL]: The specified address is bad or is not available from the local machine.
[EADDRINUSE]: The specified address is already in use.
[EINVAL]: The socket is already bound to an address, the socket has been shut down or addrlen is a bad value.
[EAFNOSUPPORT]: The requested address does not match the address family of this socket.
[EACCES]: The requested address is protected, and the current user has inadequate permission to access it. (This error can be returned by AF_INET only.)
[EFAULT]: The addr parameter is not a valid pointer.
[EOPNOTSUPP]: The socket whose descriptor is s is of a type that does not support address binding.
[ENOBUFS]: Insufficient buffer memory is available. The bind cannot complete.
[EDESTADDREQ]: No addr parameter was specified.
[ENETUNREACH]: The network is not reachable from this host.

MPE/iX Specific

On HP-UX, when binding an AF_UNIX socket to a path name (such as /tmp/mysocket, an open file having that name is created in the file system. When the bound socket is closed, that file still exists unless it is removed or unlinked. This does not occur on MPE/iX (that is, no file is created).

On HP-UX, you are allowed to specify a specific network while binding. MPE/iX does not. The IP address portion of sockaddr for AF_INET must be zero.

Author

UCB (University of California at Berkeley)