-- Contributed by Don Berryman (berryman@orca.drep.dnd.ca)
--
-- This program is essentially RECEIVER with an extra call
-- to FILE.CONTROL.SETFL to specify non-blocking IO.

-- This program receives varing length packets sent by
-- BROADCASTER over a UDP Datagram Broadcast Socket.
-- It is only possible to have ONE RECEIVER per CPU, but
-- each CPU on a network can have its own receiver. The
-- problem is that the BIND must be to a unique address
-- and port number on a particular machine.

with text_io;
with ERROR, DEBUG, INET, NETWORK, FILE;

procedure nonblocking_receiver is
                
   package net renames network;
   package intio is new text_io.integer_io (natural);

   bufsize:    constant integer := 64;                                                                                      
   subtype buffer is string(1..bufsize);

   procedure buf_recvfrom is new file.recvfrom (buffer, false);

   port:       constant inet.ipport        := 1456;
   domain:     constant net.address_format := net.af_inet;

   sock:      file.descriptor;
   buf:       buffer := (others => ascii.nul);                
   server:    file.sockaddr (family => net.af_inet);
   client:    file.sockaddr (family => net.af_inet);
   rval:      natural := 0;
   empty:     natural := 0;

begin
                      
   sock := file.socket (domain, file.dgram);

   file.sockopt.set_rcvbuf (sock, 16384); 
   file.control.setfl (sock, file.nonblock); -- Specify non-blocking IO

   server.addr := inet.addr_any;
   server.port := port;

   file.bind (sock, server);                                         
                                                                                                  
   loop

      delay (0.1); -- Slow down a little

      buf_recvfrom (sock, buf, bufsize, file.msg_none, client, rval);

      if rval = 0 then
         empty := empty + 1;
         if empty mod 100 = 0 then text_io.put_line("Waiting for data..."); end if;
      else
         text_io.put ("#EmptyReads:"); intio.put (empty, 5);
         text_io.put (" From " & inet.ntoa(client.addr)); text_io.set_col (30); 
         text_io.put (" Bytes:"); intio.put (rval, 3);
         text_io.put (" <<<" & buf(1..rval) & ">>>");
         text_io.new_line;
         empty := 0;
      end if;

   end loop;

end nonblocking_receiver;