Server response to broadcast calls

When a procedure is known to have been called via broadcast RPC, and the called procedure determines that it cannot provide the client with a useful response, it is usually best for the server to send no reply back to the client. This reduces network traffic.

To prevent the server from replying, a remote procedure can return NULL as its result. The server code generated by rpcgen will detect this and not send out a reply.

This is an example of a procedure that replies only if it thinks it is an NFS server:

   void *
   reply_if_nfsserver_1()
   {
   	char notnull;	/* just here so we can use its address */
   

   	if (access("/etc/exports", F_OK) < 0) {
   		return (NULL);	/* prevent RPC from replying */
   	}
   	/*
   	 * assign notnull a non-null value so RPC will send out a reply
   	 */
   	return ((void *)&notnull);
   }