Question

I have implemented a simple chat program in Java . However when I run the code and try to send messages from client I get this as output on Server side

For example:

Client : hi

Server: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=2000]

I get such a response from the client for any message I send..I am basically working on localhost

Can anyone help solve my problem?

My java code :

         class Client
             {
             public static void main(String args[]) throws IOException
               {

           BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
           System.out.println("enter the key value");
           int key=Integer.parseInt(br.readLine());
           int random=(int)(Math.random()*50);
           System.out.println(random);
           int response=((int)random)%(key);
           System.out.println(key);
           System.out.println("response generated is "+response);
           System.out.println("Authentication begins");
           Socket echoSocket = new Socket("127.0.0.1", 2500);
           BufferedReader sin=new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
           PrintStream sout=new PrintStream(echoSocket.getOutputStream());
           BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
           PrintWriter out = null;
           String s;
           DataOutputStream clientout=new DataOutputStream(echoSocket.getOutputStream());
           clientout.writeInt(random);
           clientout.writeInt(key);
          clientout.writeInt(response);
          System.out.println("client is"+response);
          System.out.println("chat is started");

        while (true)
    {
        System.out.print("Client : ");
        s=stdin.readLine();
        sout.println(s);
        s=sin.readLine();
        System.out.print("Server : "+s+"\n");
        if ( s.equalsIgnoreCase("BYE") )
           break;
    }

            echoSocket.close();
            sin.close();
            sout.close();
            stdin.close();
         }
    }

          class Server
         {
            public static void main(String args[]) throws IOException
              {
              int random3=(int)(Math.random()*50);
              int response2;
              int response3;
              int random2;
              int key2;
              ServerSocket s= new ServerSocket(2500);
              Socket echoSocket=s.accept();
              DataInputStream clientin=new     DataInputStream(echoSocket.getInputStream());
              BufferedReader cin=new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
         PrintStream cout=new PrintStream(echoSocket.getOutputStream());
        BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
      String s1;
            random2=clientin.readInt();
            key2=clientin.readInt();
            response2=clientin.readInt();
            System.out.println(key2);
         response3=(random2)%(key2);
            System.out.println("server is"+response2);
            if(response2==response3)
           {
            System.out.println("client is authenticated..chat starts");
                 while (true)
       {
        s1=cin.readLine();
        if (s1.equalsIgnoreCase("END"))
        {
            cout.println("BYE");
                break;
         }
        System. out.print("Client : "+s+"\n");
        System.out.print("Server : ");
        s1=stdin.readLine();
        cout.println(s1);
       }
          }

             s.close();
               echoSocket.close();
               cin.close();
            cout.close();
            stdin.close();
         }
       }

Answer 1

You get the output because you are using the wrong variables. The variable you should print from the server is s1 and not s.

Variable s refers to the socket, that’s why you are getting the socket info instead of the client’s response

s1=cin.readLine();
if (s1.equalsIgnoreCase("END"))
{
    cout.println("BYE");
    break;
}

System. out.print("Client : "+s1+"\n"); // note that this should be s1 and not s

As a good practice, you should name your variable clearly so you and others can always read the code. Having s, s1 and so on will just get you confused later as the code gets larger. It’s also a good habit to have and make other engineers who are working with you happier 🙂