Creating a client-server chat program

Question

In a server client chat program using object streams how would i be able to send a message to all clients and a private msg to certain clients?

in my listening for connections method i accept the connection

public void listenForConnections()
{
    String sUserName="";

    try{
        do {
            System.out.println("Waiting on connections");
            Socket client = servSocket.accept();
            System.out.println("Connection From: " + client.getInetAddress());          


            //pass message handling to thread and listen
            ClientHandler handler = new ClientHandler(client,this);
            handler.start();//As usual, this method calls run.                

        } while (true);
    }
    catch(Exception e){
        e.printStackTrace();
    }
}

Then i pass this client to a thread in the server to handle message exhanges;

i,e;

  //pass message handling to thread and listen ClientHandler handler = new ClientHandler(client,this); handler.start();//As usual, this method calls run. 

How and where do i keep a list of connected clients?

i thought of a hastable with the key being the username and ObjectOutPutStream. And to then read object being sent after the connection was accepted but i ran into problems. The message was a login command giving the username and a command LOGIN

My code became;

System.out.println("Waiting on connections"); Socket client = servSocket.accept(); System.out.println("Connection From: " + client.getInetAddress());

  ObjectOutputStream clientOOS = new ObjectOutputStream(client.getOutputStream()); outputStreams.put(sUserName, oos ); //big problem here //serializeation /*ois = new ObjectInputStream(client.getInputStream()); oos = new ObjectOutputStream(client.getOutputStream()); //ask for the username /authenticate System.out.println("SERVER: getting username"); myMessage inMessageLogin = (myMessage) ois.readObject(); if(inMessageLogin.getCOMMAND()==ServerCommands.CMD_LOGIN) { sUserName=inMessageLogin.getsUserName(); System.out.println("SERVED User " + sUserName + " connected."); //save stream outputStreams.put(sUserName, oos ); //oos.close(); //oos.flush(); //ois.close(); ois=null; //oos=null; } 

            //end of problem!!!!!*/

Which i commented out as it gave errors about corrupted streams, any ideas?

Thanks

To send a message to the server from client;

 //default cmd is to send to all public void sendMessage(String sText,int iCommand) { System.out.println("sendMessage"); outMessage=new myMessage(); outMessage.setsUserName(sCurrentUser); //set command outMessage.setCOMMAND(iCommand); outMessage.setsMessage(sText); System.out.println("send msg" + outMessage.displayMessage()); try { oos.writeObject(outMessage); oos.flush(); oos.reset(); //clear up send message from txbox txtMessage.setText(""); } catch (IOException ex) { Logger.getLogger(myClientGUI.class.getName()).log(Level.SEVERE, null, 

ex); } }

client code to connect to server;

 public void connectToServer() { String sServer=txtServer.getText(); PORT=Integer.parseInt(txtPort.getText()); try { //host = InetAddress.getByName("localhost");//InetAddress.getLocalHost(); host = InetAddress.getByName(sServer); clientSocket = new Socket(host, PORT); } catch (Exception e){ e.printStackTrace(); } } public boolean createStreams() { try{ //serial //******************************************************************************* // open I/O streams for objects - serialization streams oos = new ObjectOutputStream(clientSocket.getOutputStream()); ois = new ObjectInputStream(clientSocket.getInputStream()); return true; } catch(Exception e) { e.printStackTrace(); return false; } } 

Answer 1

Following code works perfectly well for me. Note that Server class must have access to Message class in it's classpath and that Message class implements Serializable .

Client:

class Client {
    private Socket clientSocket;

    public void connectToServer()
    {
        String sServer="localhost";
        int PORT = 8181;
        try {
            InetAddress host = InetAddress.getByName(sServer);
            clientSocket = new Socket(host, PORT);
        }
        catch (Exception e){
            e.printStackTrace();
        }
    }

    public void sendMessage(String sText,int iCommand) throws IOException {
        Message outMessage = new Message();

        outMessage.setCOMMAND(iCommand);
        outMessage.setsMessage(sText);

        ObjectOutputStream oos = new ObjectOutputStream(clientSocket.getOutputStream());
        try {
            oos.writeObject(outMessage);
            oos.flush();
            oos.reset();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Client c = new Client();
        c.connectToServer();
        try {
            c.sendMessage("test message", 42);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class Message implements Serializable {
    private int iCommand;
    private String sText;

    public void setCOMMAND(int iCommand) {
        this.iCommand = iCommand;
    }

    public void setsMessage(String sText) {
        this.sText = sText;
    }

    @Override
    public String toString() {
        return "Message{" +
                "iCommand=" + iCommand +
                ", sText='" + sText + '\'' +
                '}';
    }
}

Server:

class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8181);

        do {
            Socket s = serverSocket.accept();
            try {
                processClient(s);
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        } while (true);
    }

    private static void processClient(Socket s) throws IOException, ClassNotFoundException {
        ObjectInputStream ois = new ObjectInputStream(s.getInputStream());
        Message message = (Message) ois.readObject();
        System.out.println(message.toString());
    }
}