应用程序挂在套接字上，无法在服务器端读取客户端数据

Question

I am trying to implement a client server socket connection where i am passing commands like ls/pwd over the GUI and I use an url(localhost) to establish the server connection at the port. Although i am able to establish a connection with client ,the code does not proceed beyond the Client Connection accepted state. Ie it does not read the input at the server end which was sent by the client over the socket. Below are my three classes, Mainserver, ClientHandler(this handles the thread connections for the server)and the Client.

This is the Client Action button performed code:

   private void jButton1ActionPerformed(java.awt.event.ActionEventevt)      {                                         

            command = jTextField1.getText();
            String url = jTextField3.getText();
            try {
                System.out.println("Before socket connection");
                Socket socket = new Socket(url, 9002);
                System.out.println("After socket connection");
                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

                BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                System.out.println("After Buffered readers");
                System.out.println("After getting streams");

                if (socket != null) {
                    try {
                        int x = Integer.parseInt(command);
                        flag = 1;
                    } catch (Exception e) {
                        flag = 0;
                    }
                    if (flag == 0) {
                        String[] cmd = {"/bin/sh", "-c", command};

                        System.out.println("the value of command in GUI class is " + Arrays.toString(cmd));
                        try {

                            String commd = Arrays.toString(cmd);
                            System.out.println(commd);

                            out.write(commd);
                            input = in.readLine();
                        }
                        catch (IOException ex1)
                                {
                            Logger.getLogger(TestGUI.class.getName()).log(Level.SEVERE, null, ex1);
                                    }

                        jTextField2.setText(input.toString());

                    }
                }

            }//try end of the first one
            catch (IOException ex) {
                Logger.getLogger(TestGUI.class.getName()).log(Level.SEVERE, null, ex);
            }

The server class:

public class ServerMain {



    public static void main(String[] args) throws IOException, InterruptedException {

        int number, temp;
        try {

            ServerSocket serverSocket = new ServerSocket(9002);
            System.out.println("server has been started in the server");
            System.out.println("Server is waiting connection at" + InetAddress.getLocalHost().getCanonicalHostName() + "port" + serverSocket.getLocalPort());

            while (true) {
                Socket socket = serverSocket.accept();

                System.out.println("Client Connection Accepted");

                //pass on handling on this client to a thread
                (new ClientHandler(socket)).start();

            }
        } catch (Exception e) {
            System.err.println("Server already in use");
            System.exit(-1);
        }
    }
}

The client Handler for the Server:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
/**
 *
 * @author ameerah
 */
public class ClientHandler extends Thread {

    private static int BUFSIZE = 1024;

    private StringBuffer result;
    ServerSocket serverSocket;
    String serverText;
    StringBuffer output = new StringBuffer();
    private Object serversocket;

    public Socket getSock() {
        return sock;
    }

    public void setSock(Socket sock) {
        this.sock = sock;
    }

    Socket sock;

    public ClientHandler(Socket sock) {
        this.sock = sock;
    }

    @Override
    public void run() {
        PrintWriter outWriter = null;
        try {
            BufferedReader myInput = new BufferedReader(new InputStreamReader(sock.getInputStream()));
            outWriter = new PrintWriter(sock.getOutputStream());
            System.out.println(
                    "before accepting the command in server");
            String inputLine;
            while ((inputLine = myInput.readLine()) != null) //String command = myInput.readLine();
            {
                System.out.println(inputLine);

                String result = "";
                try {
                    result = executeCommand(inputLine);
                } catch (IOException ex) {
                    Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
                } catch (InterruptedException ex) {
                    Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
                }
                System.out.println(result);
                outWriter.write(result);
            }
        } catch (IOException ex) {
            Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            outWriter.close();
        }
    }

    public String executeCommand(String cmd)
            throws IOException, InterruptedException {
        try {

            Process p = Runtime.getRuntime().exec(cmd);
            p.waitFor();
            BufferedReader reader
                    = new BufferedReader(new InputStreamReader(p.getInputStream()));
            System.out.println("Inside the execute method");
            String line = "";
            while ((line = reader.readLine()) != null) {

                output.append(line + "\n");
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return output.toString();

    }

}

I have been at it for some time, and tried using different streams such as ObjectInputStream, ObjectOutputStream, but the code hangs each time. I cannot see at this point where Im going wrong :( I've searched in several forums but I do not still get an idea where Im going wrong here.Would appreciate any help.! Best Regards

Answer 1

It was the readLine() which was expecting '\\n' at the end. Therefore once i appended '\\n' at the end and added out.flush() it was able to read and not keep hanging waiting for more inputs, and now the application is working. Thank you very much for your helpful suggestions. The out.flush() advice proved to be very helpful.

Answer 2

Few tips to isolate the problem.

1. Check the value of command and catch Exception stack trace.

2. After out.write(commd); : add one more line out.flush(); After flush, server will get the data from client. Same is the case with outWriter. flush() should be called on outWriter after writing the data.

Answer 3

You are looking for an end of line to end your input loop but you are using write.

Change your send data statements to use println.

Client:

    out.println(commd);

Server:

     outWriter.println(result);