Question

Hello guys I am trying to do an echo Server by java but it is nnot working .. .I don’t know why .. but it seems like the server is waiting the client and the client is waiting the server … so they can’t deliver the infromation to each other ..

here is the code
for the Server

    ServerSocket server = null;
        try {
             server = new ServerSocket(3333);
              System.out.println("Listening on 3333");
    } catch (IOException ex) {
        System.out.println("Error can't connect to 3333");
        System.exit(1);
    }

        Socket clientSocket = null;
    try {
        clientSocket = server.accept();
    } catch (IOException ex) {
        System.out.println("Accept fail");
        System.exit(1);
    }
    PrintWriter out = null;
    try {
         out = new PrintWriter(clientSocket.getOutputStream());
    } catch (IOException ex) {
        Logger.getLogger(JavaApplication20.class.getName()).log(Level.SEVERE, null, ex);
    }
    BufferedReader br = null;
    try {
        br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
    } catch (IOException ex) {
        Logger.getLogger(JavaApplication20.class.getName()).log(Level.SEVERE, null, ex);
    }
    BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));

    String inputLine, outputLine;
 while(!(inputLine=br.readLine()).equals("bye"))
            {
                out.print("echo: " + inputLine);

            }
    out.close();
    br.close();
    clientSocket.close();
    server.close();
    System.out.println("Server Exited");

and here is the code for the client

 Socket client = null;
   try {
        client = new Socket("localhost", 3333);
        System.out.println("Connected on 3333");
    } catch (UnknownHostException ex) {
        System.out.println("Couldn't connect to the server");
        System.exit(1);
    } catch (IOException ex) {
        Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
    }


    PrintWriter out = null;
    BufferedReader in = null;
    BufferedReader stdIn = null;

    try {
        out = new PrintWriter(client.getOutputStream(), true);
    } catch (IOException ex) {
        Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
    }
    try {
        in = new BufferedReader(new InputStreamReader(client.getInputStream()));
    } catch (IOException ex) {
        Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
    }
    stdIn = new BufferedReader(new InputStreamReader(System.in));

    String fromServer, fromUser;


    while((fromUser=stdIn.readLine())!=null)
        {
            System.out.println("From user: "+ fromUser);

            out.print(fromUser);
            fromServer=in.readLine();
            System.out.println(fromServer);
        }



    out.close();
    stdIn.close();
    in.close();
    client.close();

    System.out.println("client Exited");

Any Help with that ??

Answer 1

You’re sending some string from the client ("Hello" for example), and you’re trying to read it with readLine() on the server (and vice versa). readLine() will only return once it finds an EOL character, or once the input stream is closed.

Since the client doesn’t send any EOL char, the server waits indefinitely, and the client also because it waits for the answer from the server.

Send "Hello\n", and it will work better.