Develop Reference

Java StreamCorrupted when connecting more than one Client to Server

Explanation
I'm currently trying to create a Multiplayer Game with Java where up to five Players can play together.
The problem is that when I'm trying to connect multiple Clients to my Server I get an Exception and the Server doesn't work anymore.
With one Client at a time, everything works fine.
So what I need is a Server that can handle up to five players at a time and the clients should always get some new game data from the Server
every few seconds (Connected Players, etc.).
The "Game data" in the code below is the String I'm sending through the Object Stream.
Normally I would send an Object which has all the game data, but with the String, I get the same problem.
I'm struggling with the problem that only one Client can connect without any errors occurring for some days now and I didn't find a solution to my problem.
I saw that there are things like java.nio or the ExecutorService, but I didn't really understand those that much, so I don't know if they can help.
I have made a smaller program that simulates the same problem I get with my bigger program.
To Start the Server, you need to Start the GameMultiPlayerCreate.java Class, and for the Client, the Client.java class.
I'm new to Sockets so if something is unnecessary or if something can be made better please let me know.
So the Error I'm getting when I connect two or more Clients is:
java.io.StreamCorruptedException: invalid stream header: 00050131
at java.io.ObjectInputStream.readStreamHeader(Unknown Source)
at java.io.ObjectInputStream.<init>(Unknown Source)
at Server.waitForData(Server.java:89) //I highlighted that in the code with a comment
at Server.loopWaitForData(Server.java:49)
at Server.run(Server.java:34)
at java.lang.Thread.run(Unknown Source)
Code
GameMultiPlayerCreate.java: Should start the Server threads if a Client connects
public class GameMultiPlayerCreate {
ServerSocket socketServer = null;
static String settingIp = "localhost";
static String settingPort = "22222";
static byte settingPlayers = 5;
public static int connectedPlayers = 0;
public static void main(String[] args) {
try {
GameMultiPlayerCreate objGameMultiPlayerCreate = new GameMultiPlayerCreate();
objGameMultiPlayerCreate.createServer();
} catch (NumberFormatException | IOException | InterruptedException e) {
e.printStackTrace();
}
}
public void createServer() throws NumberFormatException, UnknownHostException, IOException, InterruptedException {
while (connectedPlayers < settingPlayers) {
socketServer = new ServerSocket(Integer.parseInt(settingPort), 8, InetAddress.getByName(settingIp));
System.out.println("Server is waiting for connection...");
Socket socket = socketServer.accept();
new Thread(new Server(socket)).start();
Thread.sleep(5000);
socketServer.close();
}
}
}
Server.java: This is the Class of which a new Thread should be created for each connected Client (Client Handler)
public class Server implements Runnable {
protected static Socket socket = null;
private int loops;
private int maxLoops = 10;
private int timeout = 10000;
protected static boolean killThread = false;
private boolean authenticated = true; //true for testing
protected static String ip;
protected static int port;
public Server(Socket socket) throws IOException {
Server.socket = socket;
}
public void run() {
try {
socket.setSoTimeout(timeout);
} catch (SocketException e) {
System.out.println("Error while trying to set Socket timeout. ");
System.out.println("Closing Thread..." + Thread.currentThread());
disconnectClient();
}
if (!killThread) {
GameMultiPlayerCreate.connectedPlayers = GameMultiPlayerCreate.connectedPlayers + 1;
loopWaitForData();
}
}
private void disconnectClient() {
System.out.println("Kicking Client... " + Thread.currentThread());
killThread = true;
GameMultiPlayerCreate.connectedPlayers = GameMultiPlayerCreate.connectedPlayers - 1;
}
public void loopWaitForData() {
while (!killThread) {
System.out.println(maxLoops + ", " + loops);
if (maxLoops - loops > 0) {
try {
waitForData();
} catch (SocketTimeoutException e) {
System.out.println("Error occurred while waiting for Data. Thread disconnected? Sending reminder. " + Thread.currentThread());
if (!authenticated) {
System.out.println("Kicking Client: Not authenticated");
disconnectClient();
} else {
commandReminder();
}
} catch (ClassNotFoundException | IOException e) {
loops = loops + 1;
System.out.println("Error occurred while waiting for Data. Waiting for more Data. " + Thread.currentThread());
e.printStackTrace();
loopWaitForData();
}
} else if (maxLoops - loops == 0) {
System.out.println("Error occurred while waiting for Data. Maximum trys reached. Disbanding connection. " + Thread.currentThread());
disconnectClient();
loops = loops + 1;
} else {
System.out.println("Closing Thread..." + Thread.currentThread());
disconnectClient();
}
}
}
private void commandReminder() {
System.out.println("Reminder");
try {
String code = new String("0");
ObjectOutputStream outputObject = new ObjectOutputStream(Server.socket.getOutputStream());
outputObject.writeObject(code);
} catch (IOException e) {
System.out.println("Error occurred while trying to authenticate Client: " + e + " in " + Thread.currentThread());
}
}
public void waitForData() throws IOException, ClassNotFoundException {
String code;
System.out.println("Waiting for Data...");
//Next line is where the error occurres
ObjectInputStream inputObject = new ObjectInputStream(socket.getInputStream());
while ((code = (String) inputObject.readObject()) != null) {
System.out.println("Received Data...");
System.out.println("Input received: " + code);
return;
}
}
}
Client.java: This is the Client
public class Client {
public static Socket socket = new Socket();
private int loops = 0;
private int maxLoops = 10;
private static boolean killThread = false;
private String ip;
private int port;
public Client(String receivedIp, String receivedPort) {
ip = receivedIp;
port = Integer.parseInt(receivedPort);
try {
System.out.println("Trying to connect to Server...");
socket.connect(new InetSocketAddress(ip, port));
System.out.println("Connected!");
} catch (IOException e) {
System.out.println("Error occurred while trying to connect to Server.");
}
loopWaitForData();
}
public static void main(String[] args) {
#SuppressWarnings("unused")
Client objClient = new Client("localhost", "22222");
}
public void loopWaitForData() {
while (!killThread) {
System.out.println(maxLoops + ", " + loops);
if (maxLoops - loops > 0) {
try {
waitForData();
} catch (IOException | ClassNotFoundException e) {
loops = loops + 1;
try {
Thread.sleep(2000);
} catch (InterruptedException e1) {
}
System.out.println("Error occurred while waiting for Data. Waiting for more Data. " + Thread.currentThread());
e.printStackTrace();
loopWaitForData();
}
} else if (maxLoops - loops == 0){
System.out.println("Error occurred while waiting for Data. Maximum trys reached. Disbanding connection. " + Thread.currentThread());
try {
socket.close();
} catch (IOException e) {
System.out.println("Failed to close Socket " + Thread.currentThread());
}
loops = loops + 1;
} else {
System.out.println("Closing Thread..." + Thread.currentThread());
killThread = true;
}
}
}
public void waitForData() throws IOException, ClassNotFoundException {
InputStream input = socket.getInputStream();
ObjectInputStream inputObject = new ObjectInputStream(input);
String code;
System.out.println("Waiting for Data...");
while ((code = (String) inputObject.readObject()) != null) {
System.out.println("Received Data...");
System.out.println("Input received: " + code);
answer();
return;
}
}
private void answer() {
try {
String code = new String("1");
ObjectOutputStream outputObject = new ObjectOutputStream(socket.getOutputStream());
outputObject.writeObject(code);
} catch (IOException e) {
System.out.println("Error occurred while trying to answer: " + e + " in " + Thread.currentThread());
}
}
}

DataInputStream not Receiving Data After Flushing DataOutputStream

So, I'm fairly new to sockets and data streams... And I am absolutely baffled by this issue I'm having. I've searched for hours trying to find a solution, assuming that other people might have had the same issue I'm having, but I've found absolutely nothing helpful so far.
I'm writing a very simple multithreaded server/client program that is supposed to open a serverSocket, and accept connections from clients, storing them in a simple arraylist (I'll change the storage process once I actually get messages to send), and then a message handler thread parses the list, and checks if a user has written to the server. If the user has written something, the program then displays the resulting message to the console. My program successfully writes to the server socket through the DataOutputStream, but when I attempt to read from the corresponding DataInputStream on the server side, it says the stream is empty, and my program will continue to loop. I've checked that the DataOutputStream receives the data through DataOutputStream.size(), and that the DataInputStream I am attempting to read data from corresponds to the correct DataOutputStream I mentioned before.
User Code:
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;
public class User {
private String hashID;
private Socket connection;
private static int hashVal = 0;
DataInputStream consoleInputStream;
String consoleInput = "";
public User(Socket conn) throws SocketException {
hashID = hashUserKey();
connection = conn;
connection.setSoTimeout(1500);
consoleInputStream = new DataInputStream(System.in);
}
private static String hashUserKey() { //placeholder for now
hashVal++;
return("Guest" + hashVal);
}
public Socket getSocket() {
return this.connection;
}
public String getID() {
return this.hashID;
}
public boolean disconnect() {
try {
consoleInputStream.close();
connection.close();
return true;
} catch (IOException e) {
System.err.println(hashID + " was unable to successfully disconnect");
return false;
}
}
public void startConnection() {
new Thread() {
#Override
public void run() {
while(!connection.isClosed()) {
try {
consoleInput = consoleInputStream.readLine();
if(consoleInput != null || consoleInput != "") {
writeToServer(consoleInput);
}
} catch (IOException e) {
System.err.println("Was not able to read console input");
}
}
System.out.println("You were disconnected, have a nice day!");
return;
}
}.start();
}
private boolean writeToServer(String toWrite) {
try {
String msg = hashID + ">>>: " + toWrite;
DataOutputStream outStream = new DataOutputStream(connection.getOutputStream());
outStream.writeUTF(toWrite + "\r\n");
outStream.flush();
consoleInput = "";
System.out.println(msg + "\t was written to " + connection.getInetAddress() + ":" + connection.getPort());
return true;
} catch (IOException e) {
System.err.println(hashID + " was unable to write to server");
return false;
}
}
#Override
public boolean equals(Object o) {
User t = (User) o;
if(t.hashID == this.hashID) {
return true;
}
return false;
}
}
Server Code:
import java.net.*;
import java.io.*;
import java.util.*;
public class TestServer {
private static ServerSocket server;
private static TestLogger logger;
private static Thread serverHandlerThread;
private static Thread messageHandlerThread;
private static ArrayList<User> users;
private static volatile boolean hasBeenStopped = false;
public static boolean startServer(int port) {
logger = new TestLogger();
logger.log("Attempting to create default shutdown behavior for server");
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
if(!hasBeenStopped) {
logger.warn("Server was shut down without running stopServer(), running by default");
stopServer();
}
}
}
);
logger.log("Shutdown behaivor created. Now attempting to set up user database"/*TODO create a real database*/);
users = new ArrayList<User>();
logger.log("Attempting to start server");
try {
server = new ServerSocket(port);
logger.log("Server successfully started at " + server.getInetAddress() + ":" + server.getLocalPort() +", now attempting to start user connection handler");
serverHandlerThread = new Thread() {
#Override
public void run() {
this.setName("serverHandlerThread");
while(!server.isClosed()) {
try {
Socket temp = server.accept();
logger.log("Connection accepted from " + temp.getInetAddress());
System.out.println("Connection accepted from " + temp.getInetAddress());
startUserConnection(new User(temp));
} catch (SocketException e) {
logger.warn("Server was closed while in accept phase");
} catch (IOException e) {
e.printStackTrace();
}
}
logger.log(this.getName() + " was stopped, server socket was closed successfully");
return;
}
};
serverHandlerThread.start();
logger.log("Server thread successfully started, listening for connections on: " + server.getInetAddress().toString() + ":" + port);
logger.log("Attempting to start message handler thread to read user inputs");
messageHandlerThread = new Thread() {
#Override
public void run() {
this.setName("messageHandlerThread");
while(!server.isClosed()) {
if(users.isEmpty()) {
continue;
}
for(int i = 0; i < users.size(); i++) {
User temp = users.get(i);
try {
System.out.println(new DataInputStream(temp.getSocket().getInputStream()).readUTF());
} catch (IOException e) {
System.err.println("Nothing to read from client: " + temp.getID());
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
};
messageHandlerThread.start();
return true;
} catch (IOException e) {
logger.error("Could not bind server socket to port.");
return false;
}
}
public static boolean stopServer() {
logger.log("Started shut down process");
if(serverHandlerThread == null || !serverHandlerThread.isAlive()) {
logger.warn("Thread has not been started yet or has already been killed");
return false;
}
else {
stopAllUserConnections();
try {
server.close();
hasBeenStopped = true;
while(serverHandlerThread.isAlive()) {
}
logger.log("Server was successfully shut down");
return true;
} catch (IOException e) {
logger.error("Could not close server socket");
return false;
}
}
}
private static void startUserConnection(User user) {
logger.log("Connected new user from " + user.getSocket().getInetAddress());
users.add(user);
System.out.println(user.getID() + " was added to list");
user.startConnection();
}
private static boolean stopUserConnection(User user) {
logger.log("Attempting to disconnect user, address: " + user.getSocket().getInetAddress());
for(User u : users) {
if(u.equals(user)) {
u.disconnect();
return true;
}
}
logger.warn("Could not find user with address: " + user.getSocket().getInetAddress());
return false;
}
private static boolean stopAllUserConnections() {
logger.log("Attempting to disconnect all users from the server");
if(users.isEmpty()) {
logger.warn("No users available to disconnect");
return false;
}
for(User u : users) {
u.disconnect();
}
users.clear();
return true;
}
public static void main(String args[]) {
startServer(*the_port*);
Client c = new Client();
c.connect("0.0.0.0", *the_port*);
}
}
Client Code:
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
public boolean connect(String serverName, int port) {
try {
System.out.println("Attempting to connect");
Socket sock = new Socket(serverName, port);
System.out.println("Connected");
return true;
} catch (UnknownHostException e) {
System.err.println("Could not resolve " + serverName + ":" + port);
}
catch (IOException e) {
e.printStackTrace();
}
return false;
}
}
So as I said above, this works fine up until I attempt to read the data written to the server. No matter what I do, the server's call to readUTF() on the socket always throws an IOException and checking the bytes ready to read by using DataInputStream.available() returns 0 as well. My sample output from my most recent run is as follows:
Attempting to connect
Connected
Connection accepted from *the_address*
Guest1 was added to list
Nothing to read from client: Guest1
Nothing to read from client: Guest1
Nothing to read from client: Guest1
test
Guest1>>>: test was written to *the_address:another_port*
Nothing to read from client: Guest1
Nothing to read from client: Guest1
Nothing to read from client: Guest1
I know my code may be terribly optimized, and I'll work on fixing that later, but right now, all I want to know is why my DataInputStream is empty after flushing the corresponding DataOutputStream, and how I can successfully send UTF data between them.

Wait Until Condition become true

I got three classes in, which are TCPClient.java, TCPProtocol.java, TCPServer.java .
*Update, i paste my full TCPServer.java as well
first, user will input the text in TCPProtocol GUI Window (by using JTextarea), and click button "Send". TCPClient will get the input from TCPProtocol if user click "send", and last will send to TCPServer. So the problem is, my TCPClient never get the input from TCPProtocol.
TCPServer.java
import java.net.*;
import java.io.*;
public class TCPServer {
public static void main(String[] args) throws IOException {
//TCP component
ServerSocket serverSocket = null;
Socket clientSocket = null;
int port = 8081;
TCPProtocol nis = new TCPProtocol();//create an object to call method in protocol class
try {
serverSocket = new ServerSocket(port);
System.out.println("Waiting for connection...");
System.out.println();
} catch (IOException e) {
System.out.println(e.toString() + " :Could not listen on port: " + port);
System.exit(1);
}
try {
clientSocket = serverSocket.accept();
System.out.println("TCP Session established.");
nis.frame.setVisible(true);
nis.frame.setAlwaysOnTop(true);
System.out.println();
} catch (IOException e) {
System.out.println(e.toString() + " :Accept failed.");
System.exit(1);
}
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine, outputLine;
outputLine = nis.processAnswer(null);//get Learn Learn English line
out.println(outputLine);//and send the line out to client
nis.Jservertxt.setText(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = nis.processAnswer(inputLine);
out.println(outputLine);
nis.Jservertxt.setText(outputLine);
if (outputLine.equalsIgnoreCase("Don't miss me! Bye Bye!"))
break;
else if (outputLine.equalsIgnoreCase("Thank For Your Guessing. Have a Nice Day =)"))
break;
}
//End connection
out.flush();
out.close();
in.close();
nis.frame.setVisible(false);
if (!clientSocket.isClosed())
clientSocket.close();
nis.frame.setVisible(false);
if (!serverSocket.isClosed())
serverSocket.close();
nis.frame.setVisible(false);
System.out.println("TCP session closed.");
}
}
Here is my code for TCPProtocol.java
public volatile boolean getPressed;
Jsend.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String Data = Jusertxt.getText();
Jusertxt.setText(null);
System.out.println(Data);
getPressed=true;
}
});
}
public boolean getPressed()
{
return getPressed;
}
i din't paste the full code here because i just show the part where do got problem.
and here is my TCPClient Code
import java.io.*;
import java.net.*;
public class TCPClient{
public static void main(String[] args) throws IOException, InterruptedException{
//TCP component
int port = 8081;
String host = "localhost";
Socket nisSocket = null;
PrintWriter out = null;
BufferedReader in = null;
TCPProtocol pro = new TCPProtocol();
try {
nisSocket = new Socket(host, port);
out = new PrintWriter(nisSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(nisSocket.getInputStream()));
} catch (UnknownHostException e) {
System.out.println(e.toString() + " :Don't know about " + host);
System.exit(1);
} catch (IOException e) {
System.out.println(e.toString() + " :Couldn't get I/O for the connection to " + host);
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer, fromUser;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equalsIgnoreCase("Don't miss me! Bye Bye!"))
break;
if (fromServer.equalsIgnoreCase("Thank For Your Guessing. Have a Nice Day =)"))
break;
if (pro.getPressed())
{
fromUser = pro.Jusertxt.getText();
if (fromUser != null) {
System.out.println("\nClient: " + fromUser);
out.println(fromUser);
}
}
System.out.println("fail liao");
}
System.out.println("try again");
//End connection
out.flush();
out.close();
in.close();
stdIn.close();
//if (!nisSocket.isClosed())
nisSocket.close();
System.out.println("TCP session closed.");
}
}
So how can i only let the TCPClient.java process if only getPressed() method was true.
I try using volatile boolean variable but not working as well. Or should i use synchronized?
Solve after change to call GUI code from server to client
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equalsIgnoreCase("Don't miss me! Bye Bye!"))
break;
if (fromServer.equalsIgnoreCase("Thank For Your Guessing. Have a Nice Day =)"))
break;
pro.frame.setVisible(true);
pro.frame.setAlwaysOnTop(true);
pro.Jservertxt.setText(fromServer);
if(pro.getPressed()){
fromUser = pro.getMessage();
if (fromUser != null) {
System.out.println("\nClient: " + fromUser);
out.println(fromUser);
}
}
}

Here is a little example of a main thread (think of it as your TCPClient) that waits until user clicks button (think of this part as your TCPProtocol):
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;
public class Test extends JFrame {
public Object lock = new Object();
private JTextArea area = new JTextArea();
public Test() {
super("test");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton send = new JButton("send");
send.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
synchronized (lock) {
lock.notify();
}
}
});
add(area);
add(send, BorderLayout.SOUTH);
}
public String pullText() {
String result = area.getText();
area.setText("");
return result;
}
public static void main(String[] args) {
Test t = new Test();
t.setSize(200, 200);
t.setVisible(true);
while (true) {
synchronized (t.lock) {
try {
t.lock.wait();
System.out.println(t.pullText());
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
Maybe you can apply a similar approach to your system.
Warning: this is just a quick and dirty example to give you the idea, please double check it. In general you should be very careful when dealing with synchronization.
EDIT:
As a starting point you can modify your TCPProtocol class (the part you posted) like this:
public volatile boolean getPressed;
private Object lock = new Object(); // added lock for wait/notify coordination
private String Data; //changed scope to make it accessible in getMessage()
Jsend.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
synchronized(lock){
Data = Jusertxt.getText(); // no more a local variable, it's an instance attribute now, see declaration above
Jusertxt.setText(null);
System.out.println(Data);
getPressed=true;
lock.notify(); // notify client that user performed action
}
});
}
public boolean getPressed(){
synchronized (lock) {
try {
lock.wait(); // wait for user to perform action...
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
return getPressed; // ...then return value (I guess getPressed will always be true at this point)
}
public String getMessage(){ // call this in TCPClient instead of pro.Jusertxt.getText()
return Data;
}
I added a lock object to enable wait/notify mechanism and applied that to your actionPerformed and getPressed methods.
I also changed the scope of Data variable and I added a public method to get its value (getMessage()). If you doublecheck your code you'll see that you will always get null from pro.Jusertxt.getText() in TCPClient.java because you set it to null in actionPerformed. So change pro.Jusertxt.getText() to pro.getMessage() in TCPClient.java.
// [...]
fromUser = pro.getMessage(); // used to be fromUser = pro.Jusertxt.getText();
// [...]
If you get this raw version to work then you can refine and refactor it to make it more clean and consistent. (for instance, I suspect you don't actually need getPressed variable as it's actually always true)
I confess I didn't test this code so you might have to fix or adjust it a little, but I hope it can clarify how I meant you could apply the code I posted to your system.
Hope it helps.
Good luck :-)

You can try this:
while (!pro.getPressed()) {
System.out.println("still not true");
Thread.sleep(1000);
}
System.out.println("getPressed is true");

java chat program via internet [closed]

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Closed 9 years ago.
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well, what i want to do is basically, to make a client server chat program that works over internet, ive done a basic one that works flawlessly over lan, but cant get it right over the internet..
Server :
public class Server extends javax.swing.JFrame {
HashMap<String,PrintWriter> map = new HashMap<String,PrintWriter>();
ArrayList clientOutputStreams = new ArrayList();
ArrayList<String> onlineUsers = new ArrayList();
int port = 5080;
Socket clientSock = null;
public class ClientHandler implements Runnable {
BufferedReader reader;
Socket sock;
PrintWriter client;
public ClientHandler(Socket clientSocket, PrintWriter user) {
// new inputStreamReader and then add it to a BufferedReader
client = user;
try {
sock = clientSocket;
InputStreamReader isReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(isReader);
System.out.println("first");
} // end try
catch (Exception ex) {
System.out.println("error beginning StreamReader");
} // end catch
} // end ClientHandler()
#Override
public void run() {
System.out.println("run method is running");
String message;
String[] data;
String connect = "Connect";
String disconnect = "Disconnect";
String chat = "Chat";
try {
while ((message = reader.readLine()) != null) {
ta1.append(message + "\n");
ta1.repaint();
System.out.println("Received: " + message);
data = message.split("#");
for (String token : data) {
System.out.println(token);
}
System.out.println(data[data.length - 1] + " datalast");
if (data[2].equals(connect)) {
tellEveryone((data[0] + "#" + data[1] + "#" + chat));
userAdd(data[0]);
map.put(data[0], client);
} else if (data[2].equals(disconnect)) {
System.out.println("barpppppppppp");
tellEveryone((data[0] + "#has disconnected." + "#" + chat));
userRemove(data[0]);
map.remove(data[0]);
} else if (data[2].equals(chat)) {
tellEveryone(message);
} else {
System.out.println("No Conditions were met.");
}
} // end while
} // end try
catch (Exception ex) {
System.out.println("lost a connection");
System.out.println(ex.getMessage());
clientOutputStreams.remove(client);
} // end catch
} // end run()
}
public void go() {
// clientOutputStreams = new ArrayList();
try {
ServerSocket serverSock = new ServerSocket(port);
System.out.println("ServerSocket Created !");
System.out.println("Started listening to port " + port);
while (true) {
// set up the server writer function and then begin at the same
// the listener using the Runnable and Thread
clientSock = serverSock.accept();
PrintWriter writer = new PrintWriter(clientSock.getOutputStream());
ta1.append(writer + " ");
ta1.repaint();
System.out.println(writer);
clientOutputStreams.add(writer);
//data_of_names_and_output_streams.add(writer.toString());
// use a Runnable to start a 'second main method that will run
// the listener
Thread listener = new Thread(new Server.ClientHandler(clientSock, writer));
listener.start();
System.out.println("Server Thread for 'new player' was started");
System.out.println("got a connection");
} // end while
} // end try
catch (Exception ex) {
System.out.println("error making a connection");
} // end catch
} // end go()
public void userAdd(String data) {
String message;
String add = "# #Connect", done = "Server# #Done";
onlineUsers.add(data);
String[] tempList = new String[(onlineUsers.size())];
onlineUsers.toArray(tempList);
for (String token : tempList) {
message = (token + add);
tellEveryone(message);
System.out.println(message);
}
tellEveryone(done);
}
public void userRemove(String data) {
System.out.println(onlineUsers.size() + " is size of online users");
System.out.println(clientOutputStreams.size() + " is size of ous");
String message;
String add = "# #Connect", done = "Server# #Done";
onlineUsers.remove(data);
String[] tempList = new String[(onlineUsers.size())];
onlineUsers.toArray(tempList);
for (String token : tempList) {
message = (token + add);
tellEveryone(message);
}
tellEveryone(done);
}
public void tellEveryone(String message) {
System.out.println(onlineUsers.size() + " is size of online users");
System.out.println(clientOutputStreams.size() + " is size of ous");
// jButton1.doClick();
// sends message to everyone connected to server
Iterator it = clientOutputStreams.iterator();
if (message.length() < 250) {
System.out.println("inside it");
while (it.hasNext()) {
try {
PrintWriter writer = (PrintWriter) it.next();
writer.println(message);
// l1.setText(message);
System.out.println("Sending " + message);
writer.flush();
} // end try
catch (Exception ex) {
System.out.println("error telling everyone");
} // end catch
}
} else {
try {
clientSock.close();
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
/**
* Creates new form Server
*/
public Server() {
initComponents();
ta1.repaint();
}
public static void main(String args[]) throws Exception {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Server().setVisible(true);
}
});
new Server().go();
}
} //end form
Client : jbutton1 is setting up connection,jbutton2 sends the message.
public class Client extends javax.swing.JFrame {
boolean sent, receive;
SimpleDateFormat sdf;
String ip;
String username;
Socket sock;
BufferedReader reader;
PrintWriter writer;
ArrayList<String> userList = new ArrayList();
Boolean isConnected = false;
DefaultListModel dlm;
public Client() {
initComponents();
dlm = (DefaultListModel) l1.getModel();
ip = JOptionPane.showInputDialog("Enter the IP of the server to connect");
}
public class IncomingReader implements Runnable {
public void run() {
String stream;
String[] data;
String done = "Done", connect = "Connect", disconnect = "Disconnect", chat = "Chat", battlerequest = "battlerequest";
try {
while ((stream = reader.readLine()) != null) {
data = stream.split("#");
System.out.println(stream + " ------------------------ data");
if (data[2].equals(chat)) {
sdf = new SimpleDateFormat("HH:mm:ss");
t.append("(" + sdf.format(new Date()) + ") " + data[0] + ": " + data[1] + "\n");
//t.setText("<html><b>hi" + 3 + 3 + "</b></html>");
} else if (data[2].equals(connect)) {
t.removeAll();
userAdd(data[0]);
} else if (data[2].equals(disconnect)) {
userRemove(data[0]);
} else if (data[2].equals(done)) {
dlm.removeAllElements();
writeUsers();
userList.clear();
} else {
System.out.println("no condition met - " + stream);
}
}
} catch (Exception ex) {
System.out.println(ex.getMessage() + " hi");
}
}
}
public void ListenThread() {
Thread IncomingReader = new Thread(new Client.IncomingReader());
IncomingReader.start();
}
public void userAdd(String data) {
userList.add(data);
}
public void userRemove(String data) {
t.setText(t1.getText() + data + " has disconnected.\n");
}
public void writeUsers() {
String[] tempList = new String[(userList.size())];
userList.toArray(tempList);
for (String token : tempList) {
//ul.append( token + "\n");
dlm.addElement(token);
// ul.setText(ul.getText() + token + '\n');
}
}
public void sendDisconnect() {
String bye = (username + "# #Disconnect");
try {
writer.println(bye); // Sends server the disconnect signal.
writer.flush(); // flushes the buffer
} catch (Exception e) {
t.append("Could not send Disconnect message.\n");
}
}
public void Disconnect() {
try {
t.append("Disconnected.\n");
sock.close();
} catch (Exception ex) {
t.append("Failed to disconnect. \n");
}
isConnected = false;
n.setEditable(true);
dlm.removeAllElements();
// ul.setText("");
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
if (isConnected == false && !n.getText().equals("")) {
username = n.getText();
n.setEditable(false);
try {
sock = new Socket(ip, 5080);
InputStreamReader streamreader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamreader);
writer = new PrintWriter(sock.getOutputStream());
writer.println(username + "#has connected.#Connect"); // Displays to everyone that user connected.
writer.flush(); // flushes the buffer
isConnected = true;
jLabel4.setText(n.getText());
//t.append( "<html><font color = \"black\"><b>Server : Welcome,</b></font></html>"+username);
//t1.setText("<html><font color=\"red\">yo</font></html>");
// Used to see if the client is connected.
} catch (Exception ex) {
t.append("Cannot Connect! Try Again. \n");
n.setEditable(true);
}
ListenThread();
} else if (isConnected == true) {
t.append("You are already connected. \n");
} else if (n.getText().equals("")) {
t.append("Enter a valid name \n");
}
}
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
String nothing = "";
if ((t1.getText()).equals(nothing)) {
t1.setText("");
t1.requestFocus();
} else {
try {
writer.println(username + "#" + t1.getText() + "#" + "Chat");
writer.flush(); // flushes the buffer
} catch (Exception ex) {
t.append("Message was not sent. \n");
}
t1.setText("");
t1.requestFocus();
}
t1.setText("");
t1.requestFocus(); // TODO add your handling code here:
}
private void dicsActionPerformed(java.awt.event.ActionEvent evt) {
sendDisconnect();
Disconnect(); // TODO add your handling code here:
}
i have also port forwarded the ports i am going to use - ie. 5080
now when my friend opens the client program from his computer from his home, i tell him to enter the ip as 192.168.1.2 coz thats what is saved when i open cmd and type ipconfig....
sometimes i think that the ip address i gave him is wrong coz 192.168.1.2 is i guess lan or internal ip address, so then, so do i do ? where do i get the correct ip address ? or is something else wrong in my code ?

192.168.1.2 is a non-routable IP. Click here to get your current external IP (unless your IP address is static, it may change periodically).
If you were to sign up for a dynamic dns service (here for example), then you could give your friend a "domain name" (e.g. something.dnsdynamic.com) and the service would update when your IP address changes.

Java - Human playable Server/Client Multiplayer

I'm currently trying to implement the game of Nim using Java, I want to be able to have one player act as the server and another as the player.
I'm fairly new to Java networking and have only had experience using basic TCP/IP where the human client connects to a computer host.
The trouble I'm having is that I need to be able to differentiate between the different players whilst implementing the protocol for the game (The protocol being the logic for the game).
As it stands I can let one player (Client) interact with the Server. All that happens is the Client can play the game but there is no oppostion (The Server merely tracks the state of the game e.g. How many sticks left, valid input etc..).
How would I go about adding a second player to take the place of the host?
Edit:
The Client and Server code has been posted, it is the code I have used and I'm quite comfortable with, the question I am asking is would it be a suitable base to implement a multi-player game or would I need to do something completely different?
My Nim Protocol: (Untested)
public class NimLogic
{
private static final int WAITING = 0;
private static final int EVALUATING = 1;
private static final int ANOTHER = 2;
private int currentState = WAITING;
private int theInput = 0;
private int totalSticks = 10;
String processInput(String input) {
String theOutput = null;
try
{
theInput = Integer.parseInt(input);
}
catch (Exception e)
{
// Ignore conversion error
}
switch (currentState)
{
case WAITING:
theOutput = "Take how many sticks?";
currentState = EVALUATING;
break;
case EVALUATING:
if(theInput == 1 | theInput == 2 | theInput == 3)
{
if (theInput < totalSticks)
{
totalSticks -= theInput;
theOutput = "There are" + totalSticks + " left.";
}
else if (theInput > totalSticks)
{
theOutput = "Error: You cannot take more sticks than that are available";
currentState = EVALUATING;
}
}
if(totalSticks == 1)
{
theOutput = "Game Over! Play again? (Yes = 1, No = 0)...";
currentState = ANOTHER;
}
break;
case ANOTHER:
if (theInput == 1)
{
totalSticks = 10;
currentState = EVALUATING;
theOutput = "Take how many sticks?";
}
else
{
theOutput = "Bye.";
}
}
return theOutput;
}
}
Thanks for all the help!
Edit:
Client
public class Client
{
#SuppressWarnings("static-access")
public static void main(String machine[])
{
Socket kkSocket = null;
PrintStream os = null;
DataInputStream is = null;
try
{
kkSocket = new Socket(machine[0], 4444);
os = new PrintStream(kkSocket.getOutputStream());
is = new DataInputStream(kkSocket.getInputStream());
}
catch(UnknownHostException e)
{
System.err.println("Socket Connect failed on " + machine[0]);
}
catch (IOException e)
{
System.err.println("Streams failed on " + machine[0]);
}
if (kkSocket != null && os != null && is != null )
{
try
{
String fromServer, fromClient;
while((fromServer = is.readLine()) != null && !fromServer.equals("Bye."))
{
fromClient = JOptionPane.showInputDialog(fromServer);
os.println(fromClient);
}
JOptionPane.showMessageDialog(null, "Goodbye, keep smiling.");
os.close();
is.close();
kkSocket.close();
}
catch (UnknownHostException e)
{
System.err.println("Can't connect to " + machine[0] + e);
}
catch (IOException e)
{
e.printStackTrace();
System.err.println("I/O failed on " +machine[0]);
}
}
}
}
Server
public class Server
{
public static void main(String arg[])
{
ServerSocket serverSocket = null;
try
{
serverSocket = new ServerSocket(4444);
}
catch (IOException e)
{
System.err.println("Can't listen on 4444 -> " + e);
System.exit(1);
}
Socket clientSocket = null;
try // allow the client to connect
{
clientSocket = serverSocket.accept();
}
catch (IOException e)
{
System.err.println("Failed accept on 4444 -> " + e);
System.exit(1);
}
try
{
DataInputStream is =
new DataInputStream(new BufferedInputStream
(clientSocket.getInputStream()));
PrintStream os =
new PrintStream(new BufferedOutputStream
(clientSocket.getOutputStream(), 1024), false);
GuessState kks = new GuessState();
String inputLine, outputLine;
outputLine = kks.processInput(null);
os.println(outputLine);
os.flush();
while((inputLine = is.readLine()) != null
&& !outputLine.equals("Bye."))
{
outputLine = kks.processInput(inputLine);
os.println(outputLine);
os.flush();
}
os.close();
is.close();
clientSocket.close();
serverSocket.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}

I'm not quite sure if I'm answering your question here, so apologies if I'm not. Also, it's been a little while since I did any Java networking code, so there might be a few wrinkles here which hopefully others can sort out.
The following is a bit of a brain dump of the changes I'd probably make, for better or worse...
Rework the networking code to accept multiple connections. Normally you'd do this by handing off the socket returned by ServerSocket.accept to a thread to process. If you were dealing with a lot of connections, you could do it using NIO instead, but that's probably too far to fast for now.
Separate the game state from the client conversation code. To keep things simple, embed the client conversation code in the thread object. The game state needs to be in an object that's shared between all the threads servicing the socket.
I'd recommend making the game state a proper 'domain object' rather than having it parsing strings etc. It should have operations like 'take(clientID, int)' rather than 'processInput'.
Consider using the observer pattern to distribute events from the domain object to the socket threads. Examples of events might be 'turnTaken' or 'gameComplete'.
Embed the notion of 'turns' into the game object, and have the server broadcast an event to the socket threads announcing whose turn it is.
Hope that gives you a starter for ten?

The server/client aspect should have no bearing on the communication of the two players. You should be able to spawn two instances of the Nim game, one that listen for an incoming connection on some port(Server), and one that connects to it (Client). Once the connection is established, you can pass Objects between the two instances over your connection that represent game information. Each instance of your Nim game is responsible for parsing that game data and running the Nim logic on it.
In essence, each instance of the game can run as a server or a client. Here's some code I wrote for Chess that should be applicable. Read through it. Elsewhere I instance a Server or Client and store it in a reference of type NetworkIdenitity.
private abstract class NetworkEntity
extends Thread {
ObjectOutputStream outputStream;
ObjectInputStream inputStream;
Socket connectionHandle;
Object messageToSend;
Object receivedMessage;
public NetworkEntity(final String name) {
super(name);
}
#Override
public abstract void run();
public void getStreams()
throws IOException {
this.outputStream = new ObjectOutputStream(this.connectionHandle.getOutputStream());
this.outputStream.flush();
this.inputStream = new ObjectInputStream(this.connectionHandle.getInputStream());
}
public void closeConnection() {
try {
if (this.outputStream != null) {
this.outputStream.close();
}
if (this.inputStream != null) {
this.inputStream.close();
}
if (this.connectionHandle != null) {
this.connectionHandle.close();
chatPanel.writeToDisplay("Connection closed with "
+ this.connectionHandle.getInetAddress().getHostName());
}
}
catch (final IOException e) {
JOptionPane.showMessageDialog(thisFrame, "Problems experienced when closing connection",
"Notification", JOptionPane.ERROR_MESSAGE);
}
}
public void processIncomingData()
throws IOException {
do {
try {
this.receivedMessage = this.inputStream.readObject();
}
catch (final ClassNotFoundException e) {
JOptionPane.showMessageDialog(thisFrame, "read() error: message from "
+ this.connectionHandle.getInetAddress().getHostName() + " not received", "Notification",
JOptionPane.ERROR_MESSAGE);
}
if (this.receivedMessage instanceof Move) {
final Move m = (Move) this.receivedMessage;
System.out.println(getName() + " got move" + m);
requestMove(Table.this.chessBoard, Table.this.currentPlayer, Table.this.currentOpponent, m, false);
repaint();
}
else if (this.receivedMessage instanceof Board) {
final Board b = (Board) this.receivedMessage;
System.out.println(getName() + " received this board:");
b.printCurrentBoardState();
// System.out.println("local copy looked like this: " );
// chessBoard.printCurrentBoardState();
// chessBoard.setGameBoard(b.getGameBoard());
// switchCurrentPlayer();
// chessBoard.updateBoardState(currentPlayer,
// currentOpponent);
repaint();
}
else if (this.receivedMessage instanceof String) {
chatPanel.writeToDisplay((String) this.receivedMessage);
}
} while (/* !message.equals("SERVER>>> TERMINATE") */true);
}
public void sendData(final Object obj_to_send) {
try {
this.outputStream.writeObject(obj_to_send);
this.outputStream.flush();
}
catch (final IOException e) {
}
}
}
private final class Client
extends NetworkEntity {
private final String hostName;
private final int serverPort;
public Client(final String host, final int port) {
super("CLIENT");
this.hostName = host;
this.serverPort = port;
}
#Override
public void run() {
try {
connectToServer();
getStreams();
processIncomingData();
}
catch (final EOFException eof) {
}
catch (final IOException ioe) {
}
catch (final NullPointerException npe) {
}
finally {
closeConnection();
}
}
private void connectToServer()
throws IOException {
try {
this.connectionHandle = new Socket(InetAddress.getByName(this.hostName), this.serverPort);
connectionEstablished = true;
chatPanel.writeToDisplay("Successfully connected to "
+ this.connectionHandle.getInetAddress().getHostName());
}
catch (final IOException e) {
chatPanel.writeToDisplay("Failed to connect to: " + this.hostName);
}
}
}
private final class Server
extends NetworkEntity {
private ServerSocket server;
private final int listenPort;
public Server(final int listen_port) {
super("SERVER");
this.listenPort = listen_port;
}
#Override
public void run() {
try {
this.server = new ServerSocket(this.listenPort, 1);
chatPanel.writeToDisplay("Listening on port " + this.listenPort);
try {
waitForConnection();
getStreams();
processIncomingData();
}
catch (final EOFException eof) {
// System.out.println(getName() + "exception: " +eof);
// eof.printStackTrace();
}
catch (final IOException ioe) {
// System.out.println(getName() + "exception: " +ioe);
// ioe.printStackTrace();
}
finally {
closeConnection();
}
}
catch (final IOException e) {
JOptionPane.showMessageDialog(thisFrame, "Network Error: " + e, "Notification",
JOptionPane.ERROR_MESSAGE);
}
}
private void waitForConnection()
throws IOException {
this.connectionHandle = this.server.accept();
connectionEstablished = true;
chatPanel.writeToDisplay("Connection received from:" + this.connectionHandle.getInetAddress().getHostName());
}
#Override
public void closeConnection() {
super.closeConnection();
try {
this.server.close();
}
catch (final IOException e) {
chatPanel.writeToDisplay(getName() + "failed to disconnect from the network");
}
}