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Thread: simple Java chatroom

  1. #1
    Junior Member
    Join Date
    Dec 2012
    Thanked 0 Times in 0 Posts

    Default simple Java chatroom

    Quite simple I want to create a chatroom that accepts multiple clients all of which can assign their own ID. Whenever they input anything it is sent to all users. Currently I have a echo client server where the client inputs something and it is echoed back. My first question is how do I allow a user to give himself a username? obviously I need a variable somewhere that accepts the name what class do you recommend I put this in? and how would I get the name itself Something like if (theInput.equalsIgnoreCase("username" : ""))

    Then all that I need to do is echo what the client says to all clients. I'm at a loss of how to do this so any advice would be much appreciated. Although I've found some tutorials and example code online I don't understand it and I don't feel comfortable using it if I don't understand even if it does work. Thanks

    Here is my code: EchoClient
    '// echo client
    import java.util.Scanner;
    import java.io.*;
    import java.net.*;
    public class EchoClient {
    public static void main(String[] args) throws IOException { 
        Socket echoSocket = null;
        //PrintWriter socketOut = null;
        try {
            echoSocket = new Socket("", 4444); // connect to self at port 4444
            System.out.println("Connected OK");
            Scanner socketIn = new Scanner(echoSocket.getInputStream());  // set up input from socket
            PrintWriter socketOut = new PrintWriter(echoSocket.getOutputStream(), true);    // set up output to socket
            Scanner kbdIn = new Scanner(System.in);     // Scanner to pick up keyboard input
            String serverResp = "";
            String userInput = kbdIn.nextLine();        // get input from the user
            while (true) {
                socketOut.println(userInput);                   // send user input to the socket
                serverResp =  socketIn.nextLine();     // get the response from the socket
                System.out.println("echoed back: " + serverResp);   // print it out
                if (serverResp.equals("Closing connection")) { break; } //break if we're done
                userInput = kbdIn.nextLine();   // get next user input
        catch (ConnectException e) {
            System.err.println("Could not connect to host");
        catch (IOException e) {
            System.err.println("Couldn't get I/O for connection");
    // multiple (threaded) server
    import java.net.ServerSocket;
    import java.net.Socket;
    public class EchoServerMult {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(4444);   // create server socket on this machine
        System.err.println("Started server listening on port 4444");
        while (true) {        // as each connection is made, pass it to a thread
            //new EchoThread(serverSocket.accept()).start();  // this is same as next 3 lines
            Socket x = serverSocket.accept();   // block until next connection
            EchoThread et = new EchoThread(x);
            System.err.println("Accepted connection from client");
    // thread to handle one echo connection
    import java.net.*;
    import java.io.*;
    import java.util.Scanner;
    public class EchoThread extends Thread {
    private Socket mySocket = null;
    public EchoThread(Socket socket) {       // constructor method
        mySocket = socket;
    public void run() {
        try {
            PrintWriter out = new PrintWriter(mySocket.getOutputStream(), true);
            Scanner in = new Scanner(mySocket.getInputStream());
            String inputLine;
            while (true) {
                inputLine = in.nextLine();      
                if (inputLine.equalsIgnoreCase("Bye")) {
                    out.println("Closing connection");
                } else {
        } catch (Exception e) {
            System.err.println("Connection reset");   // bad error (client died?)

  2. #2
    Super Moderator Norm's Avatar
    Join Date
    May 2010
    Eastern Florida
    Thanked 2,273 Times in 2,244 Posts

    Default Re: simple Java chatroom

    how do I allow a user to give himself a username?
    Have a menu item that calls a listener and prompt the user using a JOptionPane class method.

    echo what the client says to all clients.
    Have a list of clients that are connected, iterate through the list and send the message to everyone in the list.
    If you don't understand my answer, don't ignore it, ask a question.

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