Kryonet客户端连接问题Java

Question

I have a kryonet client/server that work find.. well mostly. The client remains idle and eventually disconnects after awhile but thats not the issue i'm trying to solve currently. Currently, the server and client can establish a connection and send data back and forth(Before the client times out) as long as the client and server are on the same computer. If you try to connect to a different computer on the LAN the connection times out and fails.

So here's my question(s):

1. What would be a possible cause for the connection issue?

2. What is the proper way to keep a client alive? ( secondary goal but if you know it, that'd be great)

*I'm using LibGDX and Kryonet for this. As far as I know, they shouldn't have any conflicts.

Server:

package com.me.mygdxgame;
import java.io.IOException;
import java.util.ArrayList;

import com.badlogic.gdx.math.Vector2;
import com.esotericsoftware.kryonet.Connection;
import com.esotericsoftware.kryonet.Listener;
import com.esotericsoftware.kryonet.Server;
import com.me.mygdxgame.Network.Obstacles;

public class GameServer {
    Server server;

    public GameServer () throws IOException {
        server = new Server() {
            protected Connection newConnection () {
                return new PlayerConnection();
            }
        };
        Network.register(server);


        //Sends Stuff to Client
        server.addListener(new Listener() {
            public void received (Connection c, Object object) {
                PlayerConnection connection = (PlayerConnection)c;

                if (object instanceof Obstacles) {
                    if (connection.name != null) return;
                    ArrayList<Vector2> obs = ((Obstacles)object).obstacles;
                    if (obs == null) return;
                    System.out.println("Obstacles recieved.");
                    for(int i = 0; i < obs.size(); i++) 
                        System.out.println("Obstacle " + i + "- x: " + obs.get(i).x  );
                    return;
                }
            }
        });


        server.bind(Network.port);
        server.start();

    }

    public void sendAll () { //Send out data
        Obstacles ob = new Obstacles();
        ob.obstacles = new ArrayList<Vector2>();
        for(int i =0; i < Map.obstacles.size(); i++){
            ob.obstacles.add(new Vector2(Map.obstacles.get(i).x,Map.obstacles.get(i).y));
        }
        server.sendToAllTCP(ob);
    }

    static class PlayerConnection extends Connection {
        public String name;
    }
}

Client:

package com.me.mygdxgame;

import java.awt.EventQueue;
import java.io.IOException;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;

import com.badlogic.gdx.ApplicationListener;
import com.esotericsoftware.kryonet.Client;
import com.esotericsoftware.kryonet.Connection;
import com.esotericsoftware.kryonet.Listener;
import com.me.mygdxgame.Network.Obstacles;

public class GameClient implements ApplicationListener{
    Client client;
    String name;
    String RefreshHost;
    boolean Connected = false;
    ArrayList<String> hosts = new ArrayList<String>();
    public static String host;

    public GameClient (String host) {
        client = new Client();
        client.start();
        this.host = host;

        Network.register(client);

        client.addListener(new Listener() {
            public void connected (Connection connection) {
                System.out.println("connected");
                Connected = true;
            }

            public void received (Connection connection, Object object) {
                if (object instanceof Obstacles) {
                    Obstacles obs = (Obstacles)object;
                    System.out.println("Obstacle recieved on client - " + obs.obstacles.size());
                    client.sendTCP(obs);
                    System.out.println("Obstacles sent back.");
                    return;
                }else {
                    System.out.println("invalid packet");
                }
            }

            public void disconnected (Connection connection) {
                EventQueue.invokeLater(new Runnable() {
                    public void run () {
                        System.out.println("closed");
                        Connected = false;
                        client.close();
                    }
                });
            }
        });

        new Thread("Connect") {
            public void run () {
                try {
                    client.connect(5000, GameClient.host, Network.port);
                    System.out.println("Connected!");
                    client.setKeepAliveTCP(NORM_PRIORITY);
                    while(Connected) {
                        //System.out.println(client.isIdle());
                    }
                    client.run();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }.start();
    }

    @Override
    public void create() {
        // TODO Auto-generated method stub

    }

    @Override
    public void resize(int width, int height) {
        // TODO Auto-generated method stub

    }

    @Override
    public void render() {
        // TODO Auto-generated method stub

    }

    @Override
    public void pause() {
        // TODO Auto-generated method stub

    }

    @Override
    public void resume() {
        // TODO Auto-generated method stub

    }

    @Override
    public void dispose() {
        // TODO Auto-generated method stub

    }
}

Answer 1

I suggest you set the host BEFORE you start the client

   public GameClient (String host) {
        client = new Client();
        this.host = host;
        client.start();

I am not familiar with kryonet Client, but it makes sense to do it that way.

Generally make sure that your client is trying to connect to the host that you have server running on...

Answer 2

One possible cause for such connection issue is a firewall blocking your Network.port

Another one, sorry but I have to ask: Is the server-app running in the other machine?

I ask because I dont'see a main function in your server code

public static void main(String[] args) throws IOException {
        Log.set(Log.LEVEL_DEBUG);
        new GameServer();
    }

I use to get running my server-app with this terminal command

java -jar myserverfile.jar 

How do you get it running in the "remote" machine?

By the way, I am using libgdx and kryonet for my game and so far I haven't get issues using them together.

In my case I have the server in a AWS instance listening for game-client testing from my computer.