Reliable UDP Protocol Implementation in Java - Why does this happen?

Question

I'm currently using a Java implementation of the Reliable UDP protocol, found here. The project has absolutely no tutorials so I have found it really hard to identify problems.

I have set up a client and server. The server runs on localhost:1234 and the client runs on localhost:1235. The server is first established, and loops listening for connections -

try {
            ReliableSocket clientSocket = server.socket.accept();
            InetSocketAddress clientAddress = (InetSocketAddress) clientSocket.getRemoteSocketAddress();

            Logger.getLogger("ServerConnectionListener").info("New Connection from "+
                    clientAddress.getHostName()+":"+clientAddress.getPort()+" Processing...");
            LessurConnectedClient client = new LessurConnectedClient(clientSocket);
            ClientCommunicationSocketListener listener = new ClientCommunicationSocketListener(this, client);
            clientSocket.addListener(listener);
        } catch (Exception e) {
            e.printStackTrace();
        }

When a connection is established, it creates a listener for events on that socket -

class ClientCommunicationSocketListener implements ReliableSocketListener {
    ServerConnectionListener connectionListener;
    LessurConnectedClient client;

    public ClientCommunicationSocketListener(ServerConnectionListener connectionListener, LessurConnectedClient client){
        this.connectionListener = connectionListener;
        this.client = client;
    }

    @Override
    public void packetReceivedInOrder() {
        connectionListener.server.handlePacket(client);
    }

    @Override
    public void packetReceivedOutOfOrder() {
        connectionListener.server.handlePacket(client);
    }
}

When a packet is received, it passes it to server.handlePacket, which performs a debug routine of printing "Packet Received!".

My client connects to the server as so -

LessurClient client = new LessurClient();
        InetSocketAddress a = (InetSocketAddress) server.getSocket().getLocalSocketAddress();
        Logger.getLogger("client-connector").info("Trying to connect to server "+
                a.getAddress().toString()+":"+
                a.getPort());
        client.connect(a.getAddress(), a.getPort());
// LessurClient.connect
    public void connect(InetAddress address, int port){
            try {
                socket = new ReliableSocket(address, port, InetAddress.getLocalHost(), 1235);
                isConnected = true;
                Logger.getLogger("LessurClient").info("Connected to server "+address.getHostAddress()+":"+port);
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

I have linked my code so when I press the key 'Z', it will send a packet to the server as so -

public void sendPacket(GamePacket packet){
        if(!isConnected){
            Logger.getLogger("LessurClient").severe("Can't send packet. Client is not connected to any server.");
            return;
        }
        try {
            OutputStream o = socket.getOutputStream();
            o.write(packet.getData());
            o.flush();
            Logger.getLogger("LessurClient").info("Sending Packet with data \""+packet.getData()+"\" to server "+socket.getInetAddress().toString()+":"+socket.getPort());
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

My problem is, after sending 32 packets, the server no longer receives packets, and after sending 64 packets, it crashes. I have investigated into the code, and it appears that its something associated with packets not being removed from the receive queue, as when I changed the _recvQueueSize variable in ReliableSocket.java:1815 from 32 to 40, I could now send 40 packets without something going wrong.

Could someone help me identify this issue? I've been looking at the code all day.

Answer 1

I managed to fix the problem.

You see, since this is an implementation of RUDP, it extends most of the Socket classes. Specifically, ReliableSocket.getInputStream(), was custom coded to a managed input stream. My problem was, I was receiving the packets, but not reading from the buffer.

When you receive a packet you're supposed to read from the buffer, otherwise the packet will not be dropped from the queue.

So all I had to do, was everytime I received a packet, read the size of the packet, and continue.