Socket Programming Using Multi-Threading in Java.

public class Server {
    public static void main(String arg[]) throws IOException {
        final int port = 4440;
        System.out.println("Server waiting for connection on port "+port);
        ServerSocket ss = new ServerSocket(port);
        Socket clientSocket = ss.accept();
        System.out.println("Recieved connection from "+clientSocket.getInetAddress()+" on port "+clientSocket.getPort());
        //create two threads to send and recieve from client
        RecieveFromClientThread recieve = new RecieveFromClientThread(clientSocket);
        Thread thread = new Thread(recieve);
        thread.start();





        SendToClientThread send = new SendToClientThread(clientSocket);
        Thread thread2 = new Thread(send);
        thread2.start();
    }

}

---

public class Client {

    public static void main(String[] args) throws IOException {
        try {
            Socket sock = new Socket("localhost",4440);
            SendThread sendThread = new SendThread(sock);
            Thread thread = new Thread(sendThread);thread.start();
            RecieveThread recieveThread = new RecieveThread(sock);
            Thread thread2 =new Thread(recieveThread);thread2.start();
        } catch (Exception e) {System.out.println(e.getMessage());}
    }

}

---

public class SendToClientThread implements Runnable {
    PrintWriter pwPrintWriter;
    Socket clientSock = null;
   
    public SendToClientThread(Socket clientSock)
    {
        this.clientSock = clientSock;
    }
    public void run() {
        try{
        pwPrintWriter =new PrintWriter(new OutputStreamWriter(this.clientSock.getOutputStream()));//get outputstream
       
        while(true)
        {
            String msgToClientString = "WWW";
            BufferedReader input = new BufferedReader(new InputStreamReader(System.in));//get userinput
           
            msgToClientString = input.readLine();//get message to send to client
           
            pwPrintWriter.println(msgToClientString);//send message to client with PrintWriter
            pwPrintWriter.flush();//flush the PrintWriter
            System.out.println("Please enter something to send back to client..");
        }//end while
        }
        catch(Exception ex){System.out.println(ex.getMessage());}   
    }//end run
}

---

public class SendThread implements Runnable {
    Socket sock=null;
    PrintWriter print=null;
    BufferedReader brinput=null;
   
    public SendThread(Socket sock) {
        this.sock = sock;
    }//end constructor
    public void run(){
        try{
        if(sock.isConnected())
        {
            System.out.println("Client connected to "+sock.getInetAddress() + " on port "+sock.getPort());
            this.print = new PrintWriter(sock.getOutputStream(), true);   
            while(true){
                System.out.println("Type your message to send to server..type 'EXIT' to exit");
                brinput = new BufferedReader(new InputStreamReader(System.in));
                String msgtoServerString=null;
                msgtoServerString = brinput.readLine();
                this.print.println(msgtoServerString);
                this.print.flush();
           
                if(msgtoServerString.equals("EXIT"))
                break;
            }//end while
        sock.close();}}catch(Exception e){System.out.println(e.getMessage());}
    }//end run method
}

---

public class RecieveThread implements Runnable {
    Socket sock=null;
    BufferedReader recieve=null;
   
    public RecieveThread(Socket sock) {
        this.sock = sock;
    }//end constructor
    public void run() {
        try{
        recieve = new BufferedReader(new InputStreamReader(this.sock.getInputStream()));//get inputstream
        String msgRecieved = null;
        while((msgRecieved = recieve.readLine())!= null)
        {
            System.out.println("From Server: " + msgRecieved);
            System.out.println("Please enter something to send to server..");
        }
        }catch(Exception e){System.out.println(e.getMessage()+" server not running.");}
    }//end run
}

---

public class RecieveFromClientThread implements Runnable {
    Socket clientSocket=null;
    BufferedReader brBufferedReader = null;
   
    public RecieveFromClientThread(Socket clientSocket)
    {
        this.clientSocket = clientSocket;
    }//end constructor
    public void run() {
        try{
        brBufferedReader = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));       
       
        String messageString;
        while(true){
        while((messageString = brBufferedReader.readLine())!= null){//assign message from client to messageString
            if(messageString.equals("EXIT"))
            {
                break;//break to close socket if EXIT
            }
            System.out.println("From Client: " + messageString);//print the message from client
            System.out.println("Please enter something to send back to client..");
        }
        this.clientSocket.close();
        System.exit(0);
    }
       
    }
    catch(Exception ex){System.out.println(ex.getMessage());}
    }
}