udp.pde

 import hypermedia.net.*;  // for UDP communication
 UDP udp;  // define the UDP object
 String message = "";

// for ip & port see elisas_synchronotron
 
 // TEST CONENCTION IN TERMINAL
 // nc -u -l 8888
 // this listens to UDP on port 8888 on its own network.

 void udpSetup() {
    udp = new UDP( this, portIncoming );  // create a new datagram connection on port 6000
    udp.log( true );     // <-- printout the connection activity
    udp.listen( true );           // and wait for incoming message
 }


  //void receive( byte[] data ) {       // <-- default handler
  void receive( byte[] data, String ip, int port ) {  // <-- extended handler
   String message = "";
   for(int i=0; i < data.length; i++) {
     message += char(data[i]);
   }
   println("Received package on "+ip+" from port "+port+": "+message);

   // Have to use byte-wise comparison of byte array "data"
   //   because "message" and a comparable string is somehow not the same

  if(Arrays.equals(data, "sync_stage0".getBytes())) {
    // Blackout
    startUpLoaded = true;
    goToStage(0);
  
  } else if(Arrays.equals(data, "sync_stage1".getBytes())) {
    // "Await input"
    startUpLoaded = true;
    goToStage(1);
  
  } else if(Arrays.equals(data, "sync_stage2".getBytes())) {
    // "startup"
    startUpLoaded = true;
    goToStage(2);
  
  } else if(Arrays.equals(data, "sync_stage3".getBytes())) {
    // Curves without user
    startUpLoaded = true;
    goToStage(3);
    popUp(">BRAINALIZER DISCONNECTED", width/4*3, 1250);
  
  } else if(Arrays.equals(data, "sync_stage4".getBytes())) {
    // Curves with user
    startUpLoaded = true;
    goToStage(4);
    popUp(">BRAINALIZER CONNECTED", width/4*3, 2500);
  
  } else if(Arrays.equals(data, "sync_stage5".getBytes())) {
    // Success!
    startUpLoaded = true;
    goToStage(5);
  
  } else if(Arrays.equals(data, "sync_stage6".getBytes())) {
    // Elisas thoughts
    startUpLoaded = true;
    goToStage(6);
  
  } else if(Arrays.equals(data, "sync_skipLoading".getBytes())) {
    // Abort loading if stuck
     println("Aborted Loading by dungeon master");
     startUpLoaded = true;
     goToStage(1);
     udp.send("sync_ready", remoteIp, remotePort);

  } else if(Arrays.equals(data, "sync_shutdown".getBytes())) {
     // Graceful shutdown
     println("Initiated graceful shutdown by dungeon master");
     // Program closes - 
     //   literal "graceful shutdown" like this: in ~/.config/lxsession/LXDE-pi/autostart
     //   it will start bash script "play_graceful_shutdown.sh" (instead of the processing sketch directly)
     //   in there it starts the processing sketch first
     //   secondly it calls "shutdown -h now". as the processing sketch is "blocking"
     //   it will wait until it terminates to call the shutdown function 
     //   https://forums.raspberrypi.com/viewtopic.php?t=267389#p1623821
     exit();

     // or
     // https://stackoverflow.com/questions/25637/shutting-down-a-computer

  } else {
    println("Message was not for me :(");
  }
 }