getsockname

   struct sockaddr_in     daddress;
   int                    dsocket, len;
   unsigned short         port;

          .
          .
   dsocket = socket ( ... );
   daddress . sin_family = AF_INET;
   daddress.sin_port = 0;
   daddress.sin_addr.s_addr =  ... ;
   bind ( ... )
          .
          .
   if (getsockname (dsocket, &daddress, &len) < 0)
   {
      /* error */
          .
   }

   port = daddress . sin_port;   /* grab the port in host byte order */

getsockopt

   getsockopt 
   (
      

      int socket, 

      int level, /* always SOL_SOCKET */ 

      int option_name, 

      char *option_value,

      size_t *option_lenth)

      
   ) 

   

• SO_ACCEPTCONN - is the socket currently in listen mode; an int value is returned.
• SO_BROADCAST - is message broadcasting supported; an int value is returned.
• SO_OOBINLINE - is received out-of-band data left inline; an int value is returned.
• SO_ERROR - reports error status; an int value is returned. value is returned.

  setsockopt

  In some cases, you will need to set a socket option in order to get the desired functionality. The syntax is:
  

     setsockopt 
     (
        
  
        int socket, 
  
        int level, 
  
        int option_name, 
  
        char *option_value,
  
        size_t option_lenth)
  
        
     ) 
  
     

  The option names include the following:
  • SO_ACCEPTCONN - is the socket currently in listen mode; an int value is returned.
  • SO_BROADCAST - is message broadcasting supported; an int value is returned.
  • SO_OOBINLINE - is received out-of-band data left inline; an int value is returned.
  • SO_ERROR - reports error status; an int value is returned. value is returned.
    
    
    For example, in the following code, the current broadcast status of a socket is queried and then reset.

       int    bstatus;
           .
           .
       getsockopt (sock, SOL_SOCKET, SO_BROADCAST, (char *) &bstatus, 
             (size_t) sizeof (int));
       printf ("The current broadcast status is %d\n", bstatus);
       bstatus = 1;   /* 1 = True, turn on broadcast */
       setsockopt (sock, SOL_SOCKET, SO_BROADCAST, (char *) &bstatus, 
             (size_t) sizeof (int));