We Keep Coding

Separating Client class from JFrame [duplicate]

A few days ago i tried to create a server - client or client Server as an experiment to learn about socket using a thread but then someone told me that i should use swingWorker. I did some research how to use and have implemented it in as practice but it still doesn't work. the swingWorker thread doesn't look like it is running even tho i get a connection and have used .excute(). If you guys can help spot where i am doing wrong that will be great. SwingWorker class is in the startSever() and startClient() method.
private void startServer() {
SwingWorker <Void, String> runningServer = new SwingWorker<Void, String>(){
protected Void doInBackground() {
try {
listeningSocket = new ServerSocket(port);
System.out.println("waiting for connection");
connection = listeningSocket.accept();
connected = true;
System.out.println("Connected");
String incomeMessage =null;
while(connected){
inStream = connection.getInputStream();
inDataStream = new DataInputStream(inStream);
if (myMessage !=null){
outStream = connection.getOutputStream();
outDataStream = new DataOutputStream(outStream);
outDataStream.writeUTF(myMessage);
}
if((incomeMessage = inDataStream.readUTF())!=null){
clientMessage = incomeMessage;
publish(clientMessage);
incomeMessage =null;
}
}
} catch (IOException e) {
clientMessage = "Connection Lost";
}
return null;
}
runningServer.execute();
}

Here's a VERY basic example.
Basically, because you program requires asynchronous communications (that is, you need to be able to read from the socket AND write to it at the same time), you need to offload each stream to a separate thread.
The management process of this example is, well, no existent. Realistically, you should have some kind of "connection" manager that would be able to cleanly close the output and input threads so that, for example, when the user types "bye", the output thread would be able to tell the connection manager that the connection should be terminated. It would then tell the input thread to stop reading any new message and terminate...
Client
public class Client {
public static void main(String[] args) {
try {
Socket master = new Socket("localhost", 8900);
new Thread(new InputHandler(master)).start();
new Thread(new OuputHandler(master)).start();
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static class InputHandler implements Runnable {
private Socket socket;
public InputHandler(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
boolean commune = true;
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while (commune) {
String text = reader.readLine();
System.out.println("\n<server> " + text);
if (text.toLowerCase().equals("bye")) {
commune = false;
}
}
} catch (Exception exp) {
exp.printStackTrace();
} finally {
try {
reader.close();
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
}
}
public static class OuputHandler implements Runnable {
private Socket socket;
public OuputHandler(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
boolean commune = true;
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
Scanner scanner = new Scanner(System.in);
while (commune) {
System.out.print("> ");
String text = scanner.nextLine();
writer.write(text);
writer.newLine();
writer.flush();
if (text.equalsIgnoreCase("bye")) {
commune = false;
}
}
} catch (Exception exp) {
exp.printStackTrace();
} finally {
try {
writer.close();
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
}
}
}
Server
public class Server {
public static void main(String[] args) {
try {
ServerSocket master = new ServerSocket(8900);
Socket socket = master.accept();
new Thread(new InputHandler(socket)).start();
new Thread(new OuputHandler(socket)).start();
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static class InputHandler implements Runnable {
private Socket socket;
public InputHandler(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
boolean commune = true;
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while (commune) {
String text = reader.readLine();
System.out.println("\n<client> " + text);
if (text.toLowerCase().equals("bye")) {
commune = false;
}
}
} catch (Exception exp) {
exp.printStackTrace();
} finally {
try {
reader.close();
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
}
}
public static class OuputHandler implements Runnable {
private Socket socket;
public OuputHandler(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
boolean commune = true;
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
Scanner scanner = new Scanner(System.in);
while (commune) {
System.out.print("> ");
String text = scanner.next();
writer.write(text);
writer.newLine();
writer.flush();
if (text.equalsIgnoreCase("bye")) {
commune = false;
}
}
} catch (Exception exp) {
exp.printStackTrace();
} finally {
try {
writer.close();
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
}
}
}
Update (whine)
While I have your source code in front of me...
There should very, very, rarely be a need to do textMessage.addKeyListener(this)
Because you are using a JTextField, you should be using a ActionListener instead. There are a a number of important reasons for this, but for you, the main one would be the fact that a "accept" action is Look and Feel dependent. While most systems do use Enter as there "accept" action, is not a guarantee.
Have a look at How to Write a Action Listener for more information
Given the general complexity of what you are trying to do, +1 for a overall good attempt!

Using this example, the following changes work with a single telnet client.
private PrintWriter out;
...
public void keyPressed(KeyEvent e) {
if (e.getKeyChar() == KeyEvent.VK_ENTER) {
myMessage = friendLabel + textMessage.getText();
if (out != null) {
out.println(myMessage);
}
...
}
...
protected Void doInBackground() {
try {
listeningSocket = new ServerSocket(port);
System.out.println("Waiting for connection");
connection = listeningSocket.accept();
connected = true;
System.out.println("Connected");
Scanner in = new Scanner(connection.getInputStream());
out = new PrintWriter(connection.getOutputStream(), true);
publish("Connected");
while (true) {
publish(in.nextLine());
}
} catch (IOException e) {
clientMessage = "Connection Lost";
try {
connection.close();
System.out.println("Closed");
} catch (IOException e1) {
e1.printStackTrace();
connected = false;
}
}
return null;
}

I see your server port is 8900 and your client port is 8900 too. I am not sure if it matters if the server and client are running on the same machine...

client/server connection closing causes loop error

I got to stage where client and server communicate, sending messages from and to each other.
The problem I am having is how to close the connection without causing an error?
If I terminate one of the apps (either server or client) that causes the connection to be lost, and then it causes the loop that is waiting for input to loop indefinitely and showing null's.
I tried closing sockets, buffers and even the thread, didn't work.
This is the client side
public void onClick(View view) {
try {
EditText et = (EditText) findViewById(R.id.EditText01);
String str = et.getText().toString();
PrintWriter out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
out.println(str);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
class ClientThread implements Runnable {
#Override
public void run() {
try {
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
socket = new Socket(serverAddr, SERVERPORT);
CommunicationThread commThread = new CommunicationThread(socket);
new Thread(commThread).start();
} catch (UnknownHostException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
This is the server side
class ServerThread implements Runnable {
public void run() {
Socket socket = null;
try {
serverSocket = new ServerSocket(SERVERPORT);
} catch (IOException e) {
e.printStackTrace();
}
while (!Thread.currentThread().isInterrupted()) {
try {
socket = serverSocket.accept();
CommunicationThread commThread = new CommunicationThread(
socket);
new Thread(commThread).start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Both use these classes:
class CommunicationThread implements Runnable {
private Socket clientSocket;
private BufferedReader input;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
this.input = new BufferedReader(new InputStreamReader(
this.clientSocket.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
String read = input.readLine();
updateConversationHandler.post(new updateUIThread(read));
//***HERE EXTRA BIT FOR THE SERVER
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class updateUIThread implements Runnable {
private String msg;
public updateUIThread(String str) {
this.msg = str;
}
#Override
public void run() {
text.setText(msg);
}
}
the only difference is the server has this bit where it says above ***HERE EXTRA BIT FOR THE SERVER
PrintWriter out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
out.println("Message recieved");
so basically, client connects, server accepts, then client sends message, servers receives message and shows it, and then sends "Message received" to the client, and the client shows it.
All this works fine, but once the connection is lost, they hang on showing null repeatedly, and I have to force the app to close.

You aren't checking for end of stream. If readLine() returns null, the peer has closed the connection, and you must do likewise and stop reading.
It's hard to believe you really need a new thread for every line to update the UI.

Server is only reading the first object that is sent from the client

I'm having issues sending objects to a server. Right now, I have a server setup and listening for clients. The client connects, sends a test object (just a String) and outputs it to the command line. It works for the first string sent but none after that.
Server (Hivemind.java):
// Open server socket for listening
ServerSocket ss = null;
boolean listening = true;
try {
ss = new ServerSocket(PORT_NUMBER);
} catch (IOException e) {
System.err.println("Cannot start listening on port " + PORT_NUMBER);
e.printStackTrace();
}
// While listening is true, listen for new clients
while (listening) {
Socket socket = ss.accept();
ServerDispatcher dispatcher = new ServerDispatcher(socket);
dispatcher.start();
}
// Close the socket after we are done listening
ss.close();
Server Thread (ServerDispatcher):
public ServerDispatcher(Socket socket) {
super("ServerDispatcher");
this.socket = socket;
}
public void run() {
System.out.println("Client connected");
try {
input = socket.getInputStream();
objInput = new ObjectInputStream(input);
Object obj = null;
try {
obj = (String)objInput.readObject();
} catch (ClassNotFoundException ex) {
Logger.getLogger(ServerDispatcher.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println(obj);
} catch (IOException ex) {
Logger.getLogger(ServerDispatcher.class.getName()).log(Level.SEVERE, null, ex);
}
Connection Class (HivemindConnect.java):
public HivemindConnect(int port) {
this.port = port;
url = "localhost";
}
public HivemindConnect(int port, String url) {
this.port = port;
this.url = url;
}
public void connect() {
try {
socket = new Socket(url, port);
output = socket.getOutputStream();
objOutput = new ObjectOutputStream(output);
} catch (IOException e) {
e.printStackTrace();
}
}
public void close() {
try {
objOutput.close();
output.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void send(Object obj) {
try {
objOutput.writeObject(obj);
objOutput.flush();
} catch (IOException ex) {
Logger.getLogger(HivemindConnect.class.getName()).log(Level.SEVERE, null, ex);
}
}
CustomerTopComponent:
// When the TC is opened connect to the server
#Override
public void componentOpened() {
hivemind = new HivemindConnect(9001);
hivemind.connect();
}
private void btnSendActionPerformed(java.awt.event.ActionEvent evt) {
hivemind.send(txtText.getText());
}
// When the TC is closed close the connection to the server
#Override
public void componentClosed() {
hivemind.close();
}

You need a loop like this:
while(objInput.available()>0){
Object obj = null;
obj = (String)objInput.readObject();
System.out.println(obj);}
Or something similar.

Maintain server after socket killing

So I have this simple server. What I want to do is keep the server running and waiting for another client, when I kill the clients socket (telnet -> end process).
private ServerSocket serv;
public Server() throws IOException {
try {
serv = new ServerSocket(port);
serv.setReuseAddress(true);
while(true) {
Socket sock = serv.accept();
try {
BufferedReader netIn = new BufferedReader(new InputStreamReader(sock.getInputStream()));
PrintWriter netOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(sock.getOutputStream())), true);
while(true) {
//do stuff
}
} finally {
sock.close();
}
}
} catch (SocketException e) {
recreateSocket();
} catch (IOException e) {
e.printStackTrace();
}
}
private void recreateSocket() {
try {
ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(port);
serv = socket;
} catch (IOException e) {
e.printStackTrace();
}
}
Atm it throws bindException, how to deal with it.

Add catch statement(s) to before the finally block (but don't call recreateSocket() there )
Update to clarify, something like this:
while(true) {
//do stuff
}
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
sock.close();

Start a new thread to handle each accepted connection.

The reason is that you are creating a server socket again. You don't need to do this (the previous one is still working which is why you get a bind exception). This is what you want to do:
private ServerSocket serv;
public Server(int port) throws IOException
{
try {
serv = new ServerSocket(port);
serv.setReuseAddress(true);
while(true) {
Socket sock = serv.accept();
try {
BufferedReader netIn = new BufferedReader(new InputStreamReader(sock.getInputStream()));
PrintWriter netOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(sock.getOutputStream())), true);
// do stuff
} catch(SocketException e) {
e.printStackTrace();
} finally {
sock.close();
}
}
} catch (IOException e) {
e.printStackTrace();
}
}

java.io.EOFException when trying to perform java socket operations

I'm getting the following exception for the code included below that. This works fine when the while() loop is excluded. Why is this?
Oct 6, 2011 1:19:31 AM com.mytunes.server.ServerHandler run
SEVERE: null
java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at com.mytunes.server.ServerHandler.run(ServerHandler.java:68)
Class ServerHandler:
public class ServerHandler extends Thread {
.
.
.
public ServerHandler(...){
...
}
public void run(){
try {
os = s.getOutputStream();
oos = new ObjectOutputStream(os);
is = s.getInputStream();
ois = new ObjectInputStream(is);
while(true){
msg = (Messenger) ois.readObject();
String methodType = msg.getKey();
//validating various data passed from the serialized object
if(methodType.equals("validateCard")){
} else if(methodType.equals("validatePIN")){
}
}
} catch (SQLException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
} catch (ClassNotFoundException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
} finally{
try {
ois.close();
is.close();
oos.close();
os.close();
s.close();
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
Class Server
public class Server{
...
ServerSocket ss;
...
public static void main(String args[]){
Server server = new Server();
server.init();
}
public void init(){
try {
System.out.println("Server started...");
ss = new ServerSocket(port);
System.out.println("Listening on " + ss.getInetAddress() + ":" + ss.getLocalPort());
System.out.println("Waiting for clients...");
while(true){
Socket incoming_socket = ss.accept(); // returns a Socket connection object if received
new ServerHandler(...).start();
}
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}

You keep trying to read objects forever, never breaking out of the loop. When the client closes the connection, the stream will run out of data, and the ObjectInputStream.readObject method will throw the exception you're seeing.
How many objects did you expect to be in the stream, and why are you reading past the end of them?