Question

I am modifying a tutorial I found on how to create a TCP Chat Server that accepts multiple clients. I will eventually create a client class as well, but so far I am testing it with TELNET.

I want the server to continually check for input so I can use key words to preform server functions. So string word “EXIT” to disconnect the client and the string word “Name:” to print “OK”.

This is what I was thinking but it doesn’t work:

 public void run()  
    {
         String line;
         try    
         {
            while(true)   
            {
                if (input.readline("EXIT"))//Should close and remove client
                {
                    clients.remove(this);
                    users.remove(name);
                    break;
                }
                if(input.readline("Name:"))//Should print OK with username
                {
                    System.out.println("OK");
                }
                boradcast(name,line); // method  of outer class - send messages to all
            }// end of while
         } // try
         catch(Exception e) 
         {
           System.out.println(e.getMessage());
         }
    } // end of run()
 }

}

Here is the whole server class

// Chat Server runs at port no. 9020
import java.io.*;
import java.util.*;
import java.net.*;
import static java.lang.System.out;

public class  TCPServer 
{
  Vector<String> users = new Vector<String>();
  Vector<HandleClient> clients = new Vector<HandleClient>();

  int PORT = 9020;
  int NumClients = 10;

  public void process() throws Exception  
  {
      ServerSocket server = new ServerSocket(PORT,NumClients);
      out.println("Server Connected...");
      while( true) 
      {
         Socket client = server.accept();
         HandleClient c = new HandleClient(client);
         clients.add(c);
     }  // end of while
  }

  public static void main(String ... args) throws Exception 
  {
      new TCPServer().process();
  } // end of main

  public void boradcast(String user, String message)  
  {
        // send message to all connected users
        for (HandleClient c : clients)
           if (!c.getUserName().equals(user))
           {
              c.sendMessage(user,message);
           }
  }

  class HandleClient extends Thread 
  {
    String name = "";
    BufferedReader input;
    PrintWriter output;

    public HandleClient(Socket client) throws Exception 
    {
          // get input and output streams
         input = new BufferedReader(new InputStreamReader(client.getInputStream())) ;
         output = new PrintWriter (client.getOutputStream(),true);
         output.println("Welcome to Bob's Chat Server!\n");
         // read name
         output.println("Please Enter a User Name: ");
         name  = input.readLine();
         users.add(name); // add to vector
         output.println("Welcome "+name+" we hope you enjoy your chat today");
         start();
    }

    public void sendMessage(String uname,String  msg)  
    {
        output.println( uname + ":" + msg);
    }

    public String getUserName() 
    {  
        return name; 
    }

    public void run()  
    {
         String line;
         try    
         {
            while(true)   
            {
                if (input.readline("EXIT"))
                {
                    clients.remove(this);
                    users.remove(name);
                    break;
                }
                if(input.readline(name))
                {
                    System.out.println("OK");
                }
                boradcast(name,line); // method  of outer class - send messages to all
            }// end of while
         } // try
         catch(Exception e) 
         {
           System.out.println(e.getMessage());
         }
    } // end of run()
  } // end of inner class
} // end of Server

Answer 1

Without knowing exactly what you’re looking to do when an input line equals the current username, I think this is more what you’re looking for:

    public void run(){
        try{
            while(true){
                String line = input.readLine();

                if("EXIT".equals(line)){
                    clients.remove(this);
                    users.remove(name);
                    break;
                }else if(name.equals(line)){
                    System.out.println("OK");
                }
                boradcast(name, line); // method  of outer class - send messages to all
            }// end of while
        } // try
        catch(Exception e){
            System.out.println(e.getMessage());
        }
    } // end of run()

This addresses a few issues:

• input.readline is not a method, but input.readLine is – and it doesn’t accept any parameters. (This should have shown up as a compile error.)
• You were never assigning anything to the line String.
• You were reading the line multiple times. If it didn’t match “EXIT”, you read a new line to compare against name – loosing whatever the user had entered for the previous line.