My final project for a class is to put together a game, including multiplayer. So I started trying to figure out java networking, and I'm kind of stuck.
Each of the two game clients needs to be able to send and receive messages to and from the other client.
The way I figured I would handle this is that I have a NetworkServer and NetworkClient objects that runs in their own threads.
I was thinking that I would just start them from my main game application, but I wanted to do some testing first, so I set this project up:
NetworkClient:
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.util.Timer;
import java.util.TimerTask;
public class NetworkClient extends Thread {
Socket server;
ObjectOutputStream out;
Timer timer;
public NetworkClient(String hostname, int port) throws IOException
{
server = new Socket(hostname, port);
out = new ObjectOutputStream(server.getOutputStream());
timer = new Timer();
timer.schedule(new SendTask(), 0, 1*1000);
}
public void sendData(Integer b) throws IOException {
out.writeObject(b);
}
class SendTask extends TimerTask {
Integer i = new Integer(1);
public void run() {
System.out.println("Client: Sending Integer: " + i.toString());
try {
sendData(i);
i = new Integer(i.intValue()+1);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} // run()
} // class SendTask
}
NetworkServer:
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketTimeoutException;
public class NetworkServer extends Thread {
private ServerSocket serverSocket;
private Socket client;
private Integer i;
private ObjectInputStream in;
public NetworkServer(int port) throws IOException
{
serverSocket = new ServerSocket(port);
//serverSocket.setSoTimeout(10000);
}
public void run()
{
try {
System.out.println("Waiting for client on port " + serverSocket.getLocalPort() + "...");
client = serverSocket.accept();
System.out.println("Just connected to " + client.getRemoteSocketAddress());
in = new ObjectInputStream(client.getInputStream());
} catch (IOException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
while(true)
{
try
{
i = (Integer) in.readObject();
System.out.println("Server: Received the integer: " + i.toString());
}
catch(SocketTimeoutException s)
{
System.out.println("Socket timed out!");
break;
}
catch(IOException e)
{
e.printStackTrace();
try { client.close();} catch (IOException e1) {}
break;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
Network (The thing I'm using to try and test this):
import java.io.IOException;
public class Network {
NetworkClient client;
NetworkServer server;
public Network() throws IOException {
server = new NetworkServer(6066);
server.start();
client = new NetworkClient("192.168.1.196", 6066);
client.start();
}
public static void main(String [] args)
{
try
{
Network n = new Network();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
I have the timer in there to facilitate sending data from the client to the server, which would normally be done by my game, but since I'm testing I had to have it send somehow.
When I run this where the client and server are talking to each other, I get both the Sent and Received messages.
When I put it on my laptop (and change the IP in NetworkClient to match my desktop, and vice versa on my desktop) and run it in both places, the client on the desktop sends to the server on the laptop, but the client on the laptop does not send to the server on the desktop.
And at some point during the running, I get an exception about that client's connection being reset by peer, though the working client/server connection continue.
So, I guess my question is, Does anyone know why it works in one direction but not bidirectionally?
FIXED!!
Edit: Gah, I figured it out. It had to do with the timing on starting the two servers.
I changed Network to:
import java.io.IOException;
public class Network {
NetworkClient client;
NetworkServer server;
public Network() throws IOException {
startServer();
startClient();
}
private void startServer() throws IOException {
server = new NetworkServer(6066);
server.start();
}
private void startClient(){
boolean isConnected = false;
while (!isConnected) {
try {
client = new NetworkClient("192.168.1.196", 6066);
} catch (IOException e) {
// TODO Auto-generated catch block
//e.printStackTrace();
continue;
}
isConnected = true;
}
client.start();
}
public static void main(String [] args)
{
try
{
Network n = new Network();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
Edit your Firewall. Make sure that java.exe has inbound and outbound traffic enabled. Also, add a rule to your Firewall for port 6066.
Related
so today I've tried to install Citadel Email server on a raspberry pi which went ok but unfortunantly I cannot reach it from outside LAN.
I've tried to pinpoint the problem and use scanner tools that look for open ports like these :https://www.whatsmyip.org/port-scanner/
I've verified that my public IP adress is the same as my domain returns. Which indeed it is.
I've checked port forwarding severel times.
Last but not least I've wrote this java code to have a really simple example:
package main;
import java.io.IOException;
public class Main {
public static void main(String... args){
try {
Server server = new Server(8080);
Client client = new Client(8080);
} catch (IOException e) {
e.printStackTrace();
}
}
}
package main;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private boolean stop = false;
public Server(int port) throws IOException {
ServerSocket serverSocket = new ServerSocket(port);
Runnable runnable = new Runnable() {
#Override
public void run() {
while(stop == false) {
try {
Socket socket = serverSocket.accept();
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("Hello World!");
DataInputStream inputStream = new DataInputStream(socket.getInputStream());
String input = inputStream.readUTF();
System.out.println("Client wrote: " + input);
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
};
Thread thread = new Thread(runnable, "server executor");
thread.start();
}
public void stop(){
this.stop = true;
}
}
package main;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
public class Client {
public static final String LOCALHOST = "localhost";
public static final String KIRAZUKE = "---";
public static final String PUBLIC_IP_4 = "---";
public Client(int port) {
try{
doTest(LOCALHOST, port);
} catch (IOException e) {
e.printStackTrace();
}
try{
Thread.sleep(2500);
} catch (InterruptedException e) {
e.printStackTrace();
}
try{
doTest(KIRAZUKE, port);
} catch (IOException e) {
e.printStackTrace();
}
try{
Thread.sleep(2500);
} catch (InterruptedException e) {
e.printStackTrace();
}
try{
doTest(PUBLIC_IP_4, port);
} catch (IOException e) {
e.printStackTrace();
}
}
private void doTest(String host, int port) throws IOException {
System.out.println("Opening to: " + host);
Socket socket = new Socket(host, port);
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("Hello dear Server ... calling from " + host + " ... over.");
DataInputStream inputStream = new DataInputStream(socket.getInputStream());
String string = inputStream.readUTF();
System.out.println("Response from server after " + host + " call: " + string);
}
}
So I've replaced the domain name and my public ip with dashes for privacy reasons. But what happens is that when using the localhost connection everything works fine the server prints the text sent by the client and vise versa. While using either the public IP or Domain name it fails due to time out.
What could be reasons that any incoming traffic is blocked altough port forwarding is enabled for the 8080 port (and other ports that I tried) ?
Note: I've also called my ISP, according to them they "don't block anything". Additionally I tried port forwarding port 3389 and tried remote desktop to my pi but that also failed.
Thanks in advance :)
Scenario:
a) Persistent connections
b) Manage each server-client communication individually
c) Protect System from propagating exceptions/errors
I tried to created two instances of server socket listeners using the following code :
SimpleSocketServers.java
public class SimpleSocketServers {
public static void main(String[] args) throws Exception {
int port1 = 9876;
SimpleSocketServer server1 = new SimpleSocketServer(port1);
server1.startAndRunServer();
System.out.println("Servers : server1 Listening on port: " + port1);
int port2 = 9875;
SimpleSocketServer server2 = new SimpleSocketServer(port2);
server2.startAndRunServer();
System.out.println("Servers : server2 Listening on port: " + port2);
}
}
and
SimpleSocketServer.java
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class SimpleSocketServer {
private ServerSocket serverSocket;
private int port;
public SimpleSocketServer(int port) {
this.port = port;
}
public void startAndRunServer() {
try {
System.out.println("Starting Server at port " + port + " ...");
serverSocket = new ServerSocket(port);
System.out.println("Listening for client connection ...");
Socket socket = serverSocket.accept();
RequestHandler requestHandler = new RequestHandler(socket);
requestHandler.start();
} catch (Exception e) {
e.printStackTrace();
}
}
}
class RequestHandler extends Thread {
private Socket socket;
RequestHandler(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
try {
System.out.println("Client Request Response being processed...");
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter out = new PrintWriter(socket.getOutputStream());
} catch (Exception e) {
e.printStackTrace();
}
}
}
But, it creates only one instance as control is not returning from the constructor of first instance. Is there any possibility to get back control and run both instances of server socket listeners simultaneously? (ps: Pardon me, if it is wrong or trivial!)
Use 2 Different Threads, Listening To 2 Different Ports.
Thread ServerThread1 = new Thread(new Runnable() {
#Override
public void run() {
ServerSocket ServerSocketObject = null;
while(true)
{
try {
ServerSocketObject = new ServerSocket(Your_Port_Number1);
Socket SocketObject = ServerSocketObject.accept();
// Your Code Here
SocketObject.close();
} catch (IOException e) {
try {
ServerSocketObject.close();
} catch (IOException e1) {
e1.printStackTrace();
}
e.printStackTrace();
}
}
}
});
Thread ServerThread2 = new Thread(new Runnable() {
#Override
public void run() {
ServerSocket ServerSocketObject = null;
while(true)
{
try {
ServerSocketObject = new ServerSocket(Your_Port_Number2);
Socket SocketObject = ServerSocketObject.accept();
// Your Code Here
SocketObject.close();
} catch (IOException e) {
try {
ServerSocketObject.close();
} catch (IOException e1) {
e1.printStackTrace();
}
e.printStackTrace();
}
}
}
});
ServerThread1.start();
ServerThread2.start();
You need to have SimpleSocketServer implement Runnable; start a thread with itself as the Runnable in the constructor; and run an accept() loop in the run() method. At present you're blocking in the constructor waiting for a connection, and your servers will also only handle a single connection.
The more interesting question is why you want to provide the same service on two ports.
In socket programming using Java.I want a function call to happen whenever a client connects to the server. I'm stuck up here. Any help will be appreciated.
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class NewConnectionListener implements Runnable{
public static ServerSocket serverSocket;
public NewConnectionListener(){
try {
serverSocket = new ServerSocket(500);
} catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void run() {
while(true){
try {
Socket s = serverSocket.accept();
callMethodWithNewSocket(s);
System.out.println("new Client");
} catch (IOException e) {
System.out.println("Error getting Client");
e.printStackTrace();
}
}
}
}
With this code everytime there is a new connection to port 500 on the server the method callMethodWithNewSocket(Socket s) will be called with the socket as a parameter.
I'm trying to implement OSGI bundle with network server which uses network sockets.
This is the complete source code: http://www.2shared.com/file/RMXby331/CB_27.html
This is the Activator:
package org.DX_57.osgi.CB_27.impl;
import java.util.Properties;
import org.DX_57.osgi.CB_27.api.CBridge;
import org.DX_57.osgi.CB_27.impl.EchoServer;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;
public class CBridgeApp implements BundleActivator {
public void start(BundleContext bc) throws Exception {
ServiceRegistration registerService = bc.registerService(CBridge.class.getName(), new CBridgeImpl(), new Properties());
EchoServer();
}
public void stop(BundleContext bc) throws Exception {
boolean ungetService = bc.ungetService(bc.getServiceReference(CBridge.class.getName()));
}
private void EchoServer() {
EchoServer method = new EchoServer();
}
}
This is the source code if the Java Network server:
package org.DX_57.osgi.CB_27.impl;
import java.net.*;
import java.io.*;
public class EchoServer
{
ServerSocket m_ServerSocket;
public EchoServer()
{
try
{
// Create the server socket.
m_ServerSocket = new ServerSocket(12111);
}
catch(IOException ioe)
{
System.out.println("Could not create server socket at 12111. Quitting.");
System.exit(-1);
}
System.out.println("Listening for clients on 12111...");
// Successfully created Server Socket. Now wait for connections.
int id = 0;
while(true)
{
try
{
// Accept incoming connections.
Socket clientSocket = m_ServerSocket.accept();
// accept() will block until a client connects to the server.
// If execution reaches this point, then it means that a client
// socket has been accepted.
// For each client, we will start a service thread to
// service the client requests. This is to demonstrate a
// multithreaded server, although not required for such a
// trivial application. Starting a thread also lets our
// EchoServer accept multiple connections simultaneously.
// Start a service thread
ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++);
cliThread.start();
}
catch(IOException ioe)
{
System.out.println("Exception encountered on accept. Ignoring. Stack Trace :");
ioe.printStackTrace();
}
}
}
public static void main (String[] args)
{
new EchoServer();
}
class ClientServiceThread extends Thread
{
Socket m_clientSocket;
int m_clientID = -1;
boolean m_bRunThread = true;
ClientServiceThread(Socket s, int clientID)
{
m_clientSocket = s;
m_clientID = clientID;
}
public void run()
{
// Obtain the input stream and the output stream for the socket
// A good practice is to encapsulate them with a BufferedReader
// and a PrintWriter as shown below.
BufferedReader in = null;
PrintWriter out = null;
// Print out details of this connection
System.out.println("Accepted Client : ID - " + m_clientID + " : Address - " +
m_clientSocket.getInetAddress().getHostName());
try
{
in = new BufferedReader(new InputStreamReader(m_clientSocket.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(m_clientSocket.getOutputStream()));
// At this point, we can read for input and reply with appropriate output.
// Run in a loop until m_bRunThread is set to false
while(m_bRunThread)
{
// read incoming stream
String clientCommand = in.readLine();
System.out.println("Client Says :" + clientCommand);
if(clientCommand.equalsIgnoreCase("quit"))
{
// Special command. Quit this thread
m_bRunThread = false;
System.out.print("Stopping client thread for client : " + m_clientID);
}
else
{
// Echo it back to the client.
out.println(clientCommand);
out.flush();
}
}
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
// Clean up
try
{
in.close();
out.close();
m_clientSocket.close();
System.out.println("...Stopped");
}
catch(IOException ioe)
{
ioe.printStackTrace();
}
}
}
}
}
When I try to deploy the bundle on Glassfish server the application server hangs but I can connect to the java network server using the java client. It seems that there is a infinite loop. I need help to fix the code.
Best wishes
Your bundle activator start method never returns, because you're calling constructor of your service with infinite loop. A good practice is to return as fast as possible from bundle activators.
Here is an idea how to rewrite your code:
public class EchoServer {
private volatile boolean started;
public void start() {
new Thread(new Runnable() {
#Override
public void run() {
started = true;
try {
m_ServerSocket = new ServerSocket(12111);
} catch(IOException ioe) {
System.out.println("Could not create server socket at 12111. Quitting.");
System.exit(-1);
}
System.out.println("Listening for clients on 12111...");
// Successfully created Server Socket. Now wait for connections.
int id = 0;
while (started) {
try {
Socket clientSocket = m_ServerSocket.accept();
ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++);
cliThread.start();
} catch(IOException ioe) {
System.out.println("Exception encountered on accept. Ignoring. Stack Trace :");
ioe.printStackTrace();
}
}
}
}).start();
}
public void stop() {
started = false;
}
}
Activator
public class CBridgeApp implements BundleActivator {
private EchoServer method;
public void start(BundleContext bc) throws Exception {
...
method = new EchoServer();
method.start();
}
public void stop(BundleContext bc) throws Exception {
...
method.stop();
}
}
Hello Experts
can somebody please indentify the problem with this server why this is unable to connect more then one client
import java.io.*;
import java.net.*;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.*;
public class MultithreadedServer extends Thread {
private ServerSocketChannel ssChannel;
private Thread tRunSer = new Thread(this, "ServerSelectThread");
public static void main(String argv[]) throws Exception {
new MultithreadedServer();
}
public MultithreadedServer() throws Exception {
this.start();
}
public void run() {
while (true) {
try {
ssChannel = ServerSocketChannel.open();
ssChannel.configureBlocking(false);
int port = 2345;
ssChannel.socket().bind(new InetSocketAddress(port));
} catch (Exception e) {
}
}
}
}
class Connect extends Thread {
private ServerSocketChannel ssChannel;
private SimManager SM;
private BallState BS = new BallState(10, 5);
public Connect(ServerSocketChannel ssChannel) {
this.ssChannel = ssChannel;
SM = new SimManager(BS);
SM.start();
}
public void run() {
try {
SocketChannel sChannel = ssChannel.accept();
while (true) {
ObjectOutputStream oos = new ObjectOutputStream(sChannel
.socket().getOutputStream());
oos.writeObject(BS);
System.out.println("Sending String is: '" + BS.X + "'" + BS.Y);
oos.flush();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
my intention is to send the objects on network.
please help
new code:
import java.io.*;
import java.net.*;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.*;
public class MultithreadedServer extends Thread {
private ServerSocketChannel ssChannel;
private SimManager SM;
private BallState BS = new BallState(10, 5);
private Thread tRunSer = new Thread(this, "ServerSelectThread");
public static void main(String argv[]) throws Exception {
new MultithreadedServer();
}
public MultithreadedServer() throws Exception {
this.start();
}
public void run() {
// create the server socket once
try {
ssChannel = ServerSocketChannel.open();
ssChannel.configureBlocking(false);
ssChannel.socket().bind(new InetSocketAddress(2345));
} catch (IOException e1) {
e1.printStackTrace();
}
while (true) {
// accept new connections on the socket
SocketChannel accept;
try {
accept = ssChannel.accept();
ObjectOutputStream oos;
oos = new ObjectOutputStream(accept.socket().getOutputStream());
oos.writeObject(BS);
System.out.println("Sending String is: '" + BS.X + "'" + BS.Y);
oos.flush();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
}
You are creating a new server socket for each loop iteration (using the same port over and over). You must create the server socket only once, and then accept new incoming connections.
Something like:
public void run() {
// create the server socket once
ssChannel = ServerSocketChannel.open();
ssChannel.configureBlocking(false);
ssChannel.socket().bind(new InetSocketAddress(2345));
while (true) {
// accept new connections on the socket
try {
SocketChannel accept = ssChannel.accept();
System.out.println("new client: " + accept.getRemoteAddress());
} catch (Exception e) {
System.out.println("exception: " + e.getMessage());
}
}
}
If you put something in your catch block you will probably find it yourself. (e.printStackTracer() might help for the time being).
Here is the reason for your NPE:
If this channel is in non-blocking mode then this method will immediately return null if
there are no pending connections.
This is from ServerSocketChannel.accept().
Your accept call returns null, and you then try to call a method on this null object.