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...
Related
I want to run a java server program in my ubuntu computer through terminal but the problem is that once I start the program I can not stop it (the program is running in the terminal and waiting for the client).
This is my code:
import java.net.*;
import java.io.*;
public class EchoServer2 extends Thread {
protected Socket clientSocket;
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(2000);
System.out.println("Connection Socket Created");
try {
while (true) {
System.out.println("Waiting for Connection");
new EchoServer2(serverSocket.accept());
}
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
} catch (IOException e) {
System.err.println("Could not listen on port: 2000.");
System.exit(1);
} finally {
try {
serverSocket.close();
} catch (IOException e) {
System.err.println("Could not close port: 2000.");
System.exit(1);
}
}
}
private EchoServer2(Socket clientSoc) {
clientSocket = clientSoc;
start();
}
public void run() {
System.out.println("New Communication Thread Started");
try {
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(),
true);
BufferedReader in = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println("Server: " + inputLine);
out.println(inputLine);
if (inputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
} catch (IOException e) {
System.err.println("Problem with Communication Server");
System.exit(1);
}
}
}
I know that I can kill the process but I don't want to stop the program forcefully. I want to know: how can I stop the program safely? How can I implement this in my code?
Let's get it clear, you block the main thread at client acception. It will be no real way to cleanly close the program.
My solution would be to run a separate thread, that will do the acception job.
To illustrate, here's my code:
This is the acception thread:
private static Thread acception = new Thread("Acception Thread") {
public void run() {
try {
while (true) {
System.out.println("Waiting for Connection");
new EchoServer2(serverSocket.accept());
}
-> } catch (SocketException e) {
-> if(serverSocket.isClosed())
-> System.out.println("Connection Closed.");
-> }
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
}
};
Here's the modified main method:
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(2000);
System.out.println("Connection Socket Created");
-> acception.start();
} catch (IOException e) {
System.err.println("Could not listen on port: 2000.");
System.exit(1);
}
//support to close, using the command line.
Scanner scn = new Scanner(System.in);
String s = scn.next();
while(true) {
if("quit".equals.(s)) {
try {
serverSocket.close();
} catch (IOException e) {
System.err.println("Could not close port: 2000.");
System.exit(1);
} finally {
break;
}
}
s = scn.next();
}
}
You can hit the Ctrl + C keys and it will send a SIGINT (interrupt) to your program. If you don't have specific logic to run at the program shutdown it'd probably do the job.
If you have some logic to run at program shutdown, check this answer.
Check this link http://www.oracle.com/technetwork/java/javase/signals-139944.html Should help you
Edit:
Solution 1: Add this to your main method
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("Prepare to exit");
//some cleaning up code...
}
});
Solution 2: Add another thread which waits for "exit" command, SOmething like:
new Thread() {
#Override
public void run() {
System.out.println("Type exit to exit;-)");
Console c = System.console();
String msg = c.readLine();
if (msg.equals("exit")) {
//some cleaning up code...
System.exit(0);
}
}
}.start();
Trying to write - distributive simulation framework, where program is represented by an array with moving objects, server send command to move, client answer objects out of array
Goal - server send text message to each connected client separately
- client answer
Problem - can not find a way how to implement server listening and writing to one choosed client
Is there anyone, please, who can help me or get some idea?
private ServerSocket serverSocket;
private ArrayList<BufferedReader> clientBufReaders;
private ArrayList<BufferedWriter> clientBufWriters;
public static void main(String[] args) {
Server server = new Server();
}
public Server() {
try {
this.serverSocket = new ServerSocket(23456);
this.clientBufReaders = new ArrayList<BufferedReader>();
this.clientBufWriters = new ArrayList<BufferedWriter>();
this.clients();
} catch (IOException e) {
e.printStackTrace();
}
}
private void clients() {
Thread acceptThread = new Thread(new Runnable() {
private Scanner in;
public void run() {
while (true) {
try {
Socket clientSocket = serverSocket.accept();
clientBufReaders.add(new BufferedReader(new InputStreamReader(clientSocket.getInputStream())));
clientBufWriters.add(new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream())));
this.in = new Scanner(System.in);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
);
acceptThread.start();
while (true) {
synchronized (clientBufReaders) {
for (BufferedReader in : clientBufReaders) {
try {
if (in.ready()) {
System.out.println(in.readLine());
} else {
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
I am implementing a simple client-server architecture where multiple clients should be able to connect to the server and strings could be exchanged between the server and client.
My idea is that I'll have two threads on each side: a listener, constantly checking if there is anything new in the inputstream, and a writer thread, that writes into the socket if there is something to write.
However, the second thread doesn't even start... Only the first sysout is displayed.
//start new thread to handle client input
new Thread(
new ServerWorker(clientSocket, this, this.getIdCounter())).start();
System.out.println("server side listener started");
//start new thread to handle client output
new Thread(new ServerWorkerListener(clientSocket)).start();
System.out.println("server side writer started");
Here is some code from the ServerWorker:
public void run() {
try {
OutputStream output = clientSocket.getOutputStream();
while (true) {
// output.write(("Pling!\n\n").getBytes());
for (Client tempClient : server.getClientList()) {
if ((tempClient.getId() == this.id)
&& tempClient.isShouldSend()) {
output.write((tempClient.getOutputStream() + "\n\n")
.getBytes());
tempClient.setInputStream("");
tempClient.setShouldSend(false);
}
}
}
} catch (IOException e) {
System.out.println("Error in serverWorker");
e.printStackTrace();
}
}
I really don't know what I'm missing...
Whole of ServerWorker:
public class ServerWorker implements Runnable {
protected Socket clientSocket = null;
protected String serverText = null;
protected int id;
protected Server server;
public ServerWorker(Socket clientSocket, Server server,
int id) {
this.clientSocket = clientSocket;
this.serverText = serverText;
this.id = id;
this.server = server;
}
public void run() {
try {
OutputStream output = clientSocket.getOutputStream();
while (true) {
// output.write(("Pling!\n\n").getBytes());
for (Client tempClient : server.getClientList()) {
if ((tempClient.getId() == this.id)
&& tempClient.isShouldSend()) {
output.write((tempClient.getOutputStream() + "\n\n")
.getBytes());
tempClient.setInputStream("");
tempClient.setShouldSend(false);
}
}
}
} catch (IOException e) {
System.out.println("Error in serverWorker");
e.printStackTrace();
}
}
}
Whole of ServerWorkerListener:
public class ServerWorkerListener implements Runnable {
private BufferedReader input;
private Socket clientSocket;
public ServerWorkerListener(Socket clientSocket) {
this.clientSocket = clientSocket;
run();
}
#Override
public void run() {
System.out.println("its running");
try {
BufferedReader in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
while (true) {
System.out.println("it's looping");
String inputLine = null;
if ((inputLine = in.readLine()) != null) {
JOptionPane.showMessageDialog(null, inputLine, "InfoBox: "
+ "Message from client",
JOptionPane.INFORMATION_MESSAGE);
}
}
} catch (UnknownHostException e) {
System.err.println("Don't know about client");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to client");
System.exit(1);
}
}
}
You are invoking run() inside the constructor of ServerWorkerListener, which you must not do. The new thread ought to invoke run(), otherwise, since it contains an infinite loop, it will never return from the constructor and hence never invoke the Thread’s constructor, not to speak of its start method. So removing run() the invocation from the constructor should solve the problem.
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.
/*main method*/
Server server = new Server(tcpPort);
new Thread(server).start();
try {
Thread.sleep(1000*60); /* 60 seconds*/
} catch (InterruptedException e) {
e.printStackTrace();
}
server.stop;
...
This is the code I've written. A Server thread is started, and runs for 60 seconds. How do I change this to run infinitely, ending when a user enters Enter via a BufferedReader or something.
I've tried it with
while(!input.equals("")) { /* just pseudocoded here...*/
Thread.sleep(10);
}
but this will my Server stop from working correctly. My clients won't even connect to it anymore. Have I made a design mistake or is this an easy problem to solve?
Try this basic Chatting Server that I wrote. This server simply keeps running in loop and broadcast the message send by the clients to all the other clients associated with this server.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server {
// ///----------------------------------------Instance Variable Fields
ServerSocket ss = null;
Socket incoming = null;
// ///----------------------------------------Instance Variable Fields
// ///---------------------------------------- static Variable Fields
public static ArrayList<Socket> socList = new ArrayList<Socket>();
// ///---------------------------------------- static Variable Fields
public void go() {
try {
ss = new ServerSocket(25005);
while (true) {
incoming = ss.accept();
socList.add(incoming);
System.out.println("Incoming: " + incoming);
new Thread(new ClientHandleKaro(incoming)).start();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
ss.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class ClientHandleKaro implements Runnable {
InputStream is = null;
OutputStream os = null;
InputStreamReader isr = null;
BufferedReader br = null;
PrintWriter pw = null;
boolean isDone = false;
Socket sInThread = null;
public ClientHandleKaro(Socket sxxx) {
this.sInThread = sxxx;
}
#Override
public void run() {
if (sInThread.isConnected()) {
System.out.println("Welcamu Clienta");
System.out.println(socList);
}
try {
is = sInThread.getInputStream();
System.out.println("IS: " + is);
isr = new InputStreamReader(is);
br = new BufferedReader(isr);
os = sInThread.getOutputStream();
pw = new PrintWriter(os, true);
String s = new String();
while ((!isDone) && (s = br.readLine()) != null) {
String[] asx = s.split("-");
System.out.println("On Console: " + s);
// pw.println(s);
Thread tx = new Thread(new ReplyKaroToClient(s,
this.sInThread));
tx.start();
if (asx[1].trim().equalsIgnoreCase("BYE")) {
System.out.println("I am inside Bye");
isDone = true;
}
}
} catch (IOException e) {
System.out.println("Thanks for Chatting.....");
} finally {
try {
Thread tiku = new Thread(new ByeByeKarDo(sInThread));
tiku.start();
try {
tiku.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Accha to hum Chalte hain !!!");
System.out.println(socList);
br.close();
pw.close();
sInThread.close();
} catch (IOException e) {
}
}
}
}
class ReplyKaroToClient implements Runnable {
public String mString;
public Socket mSocket;
public ReplyKaroToClient(String s, Socket sIn) {
this.mString = s;
this.mSocket = sIn;
}
#Override
public void run() {
for (Socket sRaW : socList) {
if (mSocket.equals(sRaW)) {
System.out.println("Mai same hun");
continue;
} else {
try {
new PrintWriter(sRaW.getOutputStream(), true)
.println(mString);
} catch (IOException e) {
System.out.println("Its in Catch");
}
}
}
}
}
class ByeByeKarDo implements Runnable {
Socket inCom;
public ByeByeKarDo(Socket si) {
this.inCom = si;
}
#Override
public void run() {
try {
new PrintWriter(inCom.getOutputStream(), true)
.println("You have Logged Out of Server... Thanks for ur Visit");
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
new Server().go();
}
}
Start with this SO thread: How to create a basic Java Server? . It will give you an example how to write a very simple server.
Key thing to note there is the serverSocket.accept() . It will block - in other words it will WAIT forever for a client to connect, or it will fail in the case of some error. Once a client is connected, you will get a clientSocket that you can use to read what client wrote, and also write to it.
It is really a good starting point for understanding Java network programming. However, I recommend you read more about this topic. Something like this: http://beej.us/guide/bgnet/