是否可以将小程序用作Java的服务器？

Question

I'm just getting into networking and I'm quite confused about how I can use a server from a server hosting company for a game. At the moment, the program allows a user to host the server from their computer and it works to some degree. The only problem is that when my friends connect to the game from other states their ping is super high and they lag horribly.

I'm now using a site that gives out free web hosting space. I've believe I've jumped through most of the permission hoops that I need in order to use sockets and the applet works just like it does while running on my computer.

Below is an excerpt from the Game class. If I use InetAddress.getLocalHost().getHostAddress() to get the IP, it gets the IP from the user who is using the client and makes them the server host. This works, but it doesn't solve my problem of lag.

    Game.java

    public synchronized void start() {
    running = true;

    thread = new Thread(this, NAME + "_main");
    thread.start();

    if (JOptionPane.showConfirmDialog(this, "Do you want to run the server") == 0) {
        socketServer = new GameServer(this);
        socketServer.start();
    }


    this.ipAddress = "31.170.163.198";
    //this.ipAddress = InetAddress.getByName(ipAddress).toString();

    System.out.println("IP: " + this.ipAddress);
    socketClient = new GameClient(this, this.ipAddress);//Inet4Address.getLocalHost().getHostAddress());    

    try {
        Player.setIp(Inet4Address.getLocalHost().getHostAddress());
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }
    socketClient.start();
}

I want the server that contains the jar to host the server. We all ping test each other and we mostly all get timed out, however, when we ping the server's ip we all get decent ping. When I enter the Server's IP (I find this info in the control panel) manually the server/client fail to make a connection. I've tried using both the website IP and the server IP that are provided. I've also tried using the applet.getCodeBase().getHost() in order to retrieve the IP from the server but that IP failed to send/receive data as well.

Is what I'm trying to do possible? Is the server blocking me from using it in that way? Do I need to rewrite the whole program and look into java servlets to achieve my goal?

I apologize if the question is silly. I've been working on this for the past 3-4 days with very little progress. I've searched around a bit on using a server in this manner and I've found very little on the topic.

Below are some excerpts from other relevant pieces of code.

GameClient.java

package fraccas.java2dgame.net;


public class GameClient extends Thread {

private InetAddress ipAddress;
private DatagramSocket socket;
private Game game;
public long lastPing = 0;
public static int ping = 0;

public GameClient(Game game, String ipAddress) {
    this.game = game;
    try {
        this.socket = new DatagramSocket();
        this.ipAddress = InetAddress.getByName(ipAddress);
        System.out.println("IP: " + InetAddress.getByName(ipAddress));
    } catch (SocketException e) {
        e.printStackTrace();
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }
}

public void run() {
    while (true) {
        byte[] data = new byte[1024];
        DatagramPacket packet = new DatagramPacket(data, data.length);
        try {
            socket.receive(packet);
            if (packet != null)
            {
                long current = System.currentTimeMillis();
                ping = (int) (current - lastPing);
                lastPing = current;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        this.parsePacket(packet.getData(), packet.getAddress(), packet.getPort());
    }
}

private void parsePacket(byte[] data, InetAddress address, int port) {
    String message = new String(data).trim();
    PacketTypes type = Packet.lookupPacket(message.substring(0, 2));
    Packet packet = null;
    switch (type) {
    default:
    case INVALID:
        break;
    case LOGIN:
        packet = new Packet00Login(data);
        handleLogin((Packet00Login) packet, address, port);
        break;
    case DISCONNECT:
        packet = new Packet01Disconnect(data);
        System.out.println("[" + address.getHostAddress() + ":" + port + "] "
                + ((Packet01Disconnect) packet).getUsername() + " has left the world...");
        game.level.removePlayerMP(((Packet01Disconnect) packet).getUsername());
        break;
    case MOVE:
        packet = new Packet02Move(data);
        handleMove((Packet02Move) packet);
    }
}

public void sendData(byte[] data) {
    //if (!game.isApplet) {
        DatagramPacket packet = new DatagramPacket(data, data.length, ipAddress, 3333);
        try {
            socket.send(packet);
        } catch (IOException e) {
            e.printStackTrace();
        }
   //}
}

private void handleLogin(Packet00Login packet, InetAddress address, int port) {
    System.out.println("[" + address.getHostAddress() + ":" + port + "] " + packet.getUsername()
            + " has joined the game...");
    PlayerMP player = new PlayerMP(game.level, packet.getX(), packet.getY(), packet.getUsername(), address, port);
    game.level.addEntity(player);
}

private void handleMove(Packet02Move packet) {
    this.game.level.movePlayer(packet.getUsername(), packet.getX(), packet.getY(), packet.getNumSteps(),
            packet.isMoving(), packet.getMovingDir());
}

}

GameServer.java

package fraccas.java2dgame.net;


public class GameServer extends Thread {

private DatagramSocket socket;
private Game game;
private List<PlayerMP> connectedPlayers = new ArrayList<PlayerMP>();

public GameServer(Game game) {
    this.game = game;
    try {
        this.socket = new DatagramSocket(3333);
    } catch (SocketException e) {
        e.printStackTrace();
    }
}

public void run() {
    while (true) {
        byte[] data = new byte[1024];
        DatagramPacket packet = new DatagramPacket(data, data.length);
        try {
            socket.receive(packet);
        } catch (IOException e) {
            e.printStackTrace();
        }
        this.parsePacket(packet.getData(), packet.getAddress(), packet.getPort());
    }
}

private void parsePacket(byte[] data, InetAddress address, int port) {
    String message = new String(data).trim();
    PacketTypes type = Packet.lookupPacket(message.substring(0, 2));
    Packet packet = null;
    switch (type) {
    default:
    case INVALID:
        break;
    case LOGIN:
        packet = new Packet00Login(data);
        System.out.println("[" + address.getHostAddress() + ":" + port + "] "
                + ((Packet00Login) packet).getUsername() + " has connected...");
        PlayerMP player = new PlayerMP(game.level, 100, 100, ((Packet00Login) packet).getUsername(), address, port);
        this.addConnection(player, (Packet00Login) packet);
        break;
    case DISCONNECT:
        packet = new Packet01Disconnect(data);
        System.out.println("[" + address.getHostAddress() + ":" + port + "] "
                + ((Packet01Disconnect) packet).getUsername() + " has left...");
        this.removeConnection((Packet01Disconnect) packet);
        break;
    case MOVE:
        packet = new Packet02Move(data);
        this.handleMove(((Packet02Move) packet));
    }
}

public void addConnection(PlayerMP player, Packet00Login packet) {
    boolean alreadyConnected = false;
    for (PlayerMP p : this.connectedPlayers) {
        if (player.getUsername().equalsIgnoreCase(p.getUsername())) {
            if (p.ipAddress == null) {
                p.ipAddress = player.ipAddress;
            }
            if (p.port == -1) {
                p.port = player.port;
            }
            alreadyConnected = true;
        } else {
            // relay to the current connected player that there is a new
            // player
            sendData(packet.getData(), p.ipAddress, p.port);

            // relay to the new player that the currently connect player
            // exists
            //packet = new Packet00Login(p.getUsername(), p.x, p.y);
            Packet00Login packetNew = new Packet00Login(p.getUsername(), p.x, p.y);
            sendData(packetNew.getData(), player.ipAddress, player.port);
        }
    }
    if (!alreadyConnected) {
        this.connectedPlayers.add(player);
    }
}

public void removeConnection(Packet01Disconnect packet) {
    this.connectedPlayers.remove(getPlayerMPIndex(packet.getUsername()));
    packet.writeData(this);
}

public PlayerMP getPlayerMP(String username) {
    for (PlayerMP player : this.connectedPlayers) {
        if (player.getUsername().equals(username)) {
            return player;
        }
    }
    return null;
}

public int getPlayerMPIndex(String username) {
    int index = 0;
    for (PlayerMP player : this.connectedPlayers) {
        if (player.getUsername().equals(username)) {
            break;
        }
        index++;
    }
    return index;
}

public void sendData(byte[] data, InetAddress ipAddress, int port) {
    //if (!game.isApplet) {

        DatagramPacket packet = new DatagramPacket(data, data.length, ipAddress, port);
        try {
            this.socket.send(packet);
        } catch (IOException e) {
            e.printStackTrace();
        }
    //}
}

public void sendDataToAllClients(byte[] data) {
    for (PlayerMP p : connectedPlayers) {
        sendData(data, p.ipAddress, p.port);
    }
}

private void handleMove(Packet02Move packet) {
    if (getPlayerMP(packet.getUsername()) != null) {
        int index = getPlayerMPIndex(packet.getUsername());
        PlayerMP player = this.connectedPlayers.get(index);
        player.x = packet.getX();
        player.y = packet.getY();
        player.setMoving(packet.isMoving());
        player.setMovingDir(packet.getMovingDir());
        player.setNumSteps(packet.getNumSteps());
        packet.writeData(this);
    }
}

The applet does not have any errors in the console at the moment. It simply does not send/receive the data.

http://critterisland.bugs3.com/public_html/index.html (Applet Link) http://gyazo.com/a91401545b1a741f2b9fc86471bd5762 (Image of Applet)

Thanks for you time, Fraccas

Answer 1

The problem is that you're using a web host which is only able to provide the files to users as opposed to actually being able to run the software you've created.

To run your software independently in the way you're wanting, your easiest option is to rent a virtual private server (VPS) which is located appropriately for your users. However, you'll need to be able to do some basic configuration on the VPS (such as install Java), and then run your server as a console application.

Not much code needs to be changed to get it working. You could use the same jar file for both the server and the client by adding a command line argument which only starts the server (ie "-server"). From the server computer/VPS you would then start the server by running "java -jar CritterIslandTest.jar -server" which then only starts the server and handles communication. If the command line argument is not found you can then continue with the GUI logic.