//We need to use "implements Runnable to tell Java that this is a thread
 class ClientThread implements Runnable {
 //This run method is what is executed when the thread starts
 public void run()
 {
 //Set up the PrintWriter and BufferedReader here
 while(true) {
 //Get info sent from client
 String clientInput = input.nextLine();
 //Here would would have a for loop that would send the
 //client's message to every other client connected.
 }
 }
 }

Okay, now that you know a little about threads and what we’re going to do with them lets redo the server code.

import java.net.*;
import java.util.*;
import java.io.*;

public class Server
{
    public static void main(String[] args)
    {
        new Server();
    }

    public Server()
    {
        //We need a try-catch because lots of errors can be thrown
        try {
            ServerSocket sSocket = new ServerSocket(5000);
            System.out.println("Server started at: " + new Date());


            //Loop that runs server functions
            while(true) {
                //Wait for a client to connect
                Socket socket = sSocket.accept();



                //Create a new custom thread to handle the connection
                ClientThread cT = new ClientThread(socket);

                //Start the thread!
                new Thread(cT).start();

            }
        } catch(IOException exception) {
            System.out.println("Error: " + exception);
        }
    }

    //Here we create the ClientThread inner class and have it implement Runnable
    //This means that it can be used as a thread
    class ClientThread implements Runnable
    {
        Socket threadSocket;

        //This constructor will be passed the socket
        public ClientThread(Socket socket)
        {
            //Here we set the socket to a local variable so we can use it later
            threadSocket = socket;
        }

        public void run()
        {
            //All this should look familiar
            try {
                //Create the streams
                PrintWriter output = new PrintWriter(threadSocket.getOutputStream(), true);
                BufferedReader input = new BufferedReader(new InputStreamReader(threadSocket.getInputStream()));

                //Tell the client that he/she has connected
                output.println("You have connected at: " + new Date());

                while (true) {
                    //This will wait until a line of text has been sent
                    String chatInput = input.readLine();
                    System.out.println(chatInput);
                }
            } catch(IOException exception) {
                System.out.println("Error: " + exception);
            }
        }
    }
}

The Explanation