!7

import java.nio.*;
import java.nio.channels.*;

static long timeout = 30000+10000; // idle time + latency
static ConnectedInstances cI;
static ReliableSingleThread rst = new(r update);
static int theNumber;
static int port = 6000;
static Set<AsynchronousSocketChannel> channels = synchroSet();

sclass State {
  S computerID;
  int countSeen = -1;
}

p {
  cI = new ConnectedInstances;
  cI.connected2.onChange(rst);
  
  InetSocketAddress sockAddr = new InetSocketAddress(port);
  AsynchronousServerSocketChannel serverSock =  AsynchronousServerSocketChannel.open().bind(sockAddr);
        
  //start to accept the connection from client
  serverSock.accept(serverSock, new CompletionHandler<AsynchronousSocketChannel,AsynchronousServerSocketChannel>() {
    public void completed(AsynchronousSocketChannel sockChannel, AsynchronousServerSocketChannel serverSock) {
      //a connection is accepted, start to accept next connection
      serverSock.accept(serverSock, this);
      
      channels.add(channel);
      
      //start to read message from the client
      startRead( sockChannel );
    }

    public void failed(Throwable exc, AsynchronousServerSocketChannel serverSock) {
      print("fail to accept a connection");
    }
  });
}
        
static void startRead( AsynchronousSocketChannel sockChannel) {
  final ByteBuffer buf = ByteBuffer.allocate(2048);
        
  //read message from client
  sockChannel.read(buf, sockChannel, new CompletionHandler<Int, AsynchronousSocketChannel>() {
    @Override
    public void completed(Int result, AsynchronousSocketChannel channel) {
      buf.flip();
                
      // echo the message
      startWrite(channel, buf);
                
      // start to read next message again
      startRead(channel);
    }

    @Override
    public void failed(Throwable exc, AsynchronousSocketChannel channel) {
      print( "fail to read message from client");
    }
  });
}
    
static void startWrite(AsynchronousSocketChannel sockChannel, final ByteBuffer buf) {
  sockChannel.write(buf, sockChannel, new CompletionHandler<Integer, AsynchronousSocketChannel >() {
    @Override
    public void completed(Int result, AsynchronousSocketChannel channel) {                 
      // finish to write message to client, nothing to do
      // (close socket?)
    }

    @Override
    public void failed(Throwable exc, AsynchronousSocketChannel channel) {
      print("Fail to write message to client");
    }
  });
}

html { ret "Use port " + port; }

svoid sendNumber(O ws) {
  State s = wsToState.get(ws);
  if (s != null && theNumber != s.countSeen) {
    s.countSeen = theNumber;
    print("Sending number to " + s.computerID + ": " + theNumber);
    call(ws, 'send, str(theNumber));
  }
}

svoid update {
  print("OS Instances update");
  if (webSocketManager.isEmpty()) ret;

  int value = cI.value();
  //if (value == theNumber) ret;
  theNumber = value;
  for (O ws : webSocketManager.webSockets()) pcall {
    sendNumber(ws);
  }
  print("OS Instances update done");
}

Began life as a copy of #1016453