CODEWITHSUNDEEP
javasocketstcpclient-serverreadline
Android_enthusiast
Android_enthusiast

Reputation: 903

Tcp Socket: readine hangs if used in while loop at Client : java

I have been banging my head trying to figure out what is going wrong.

I am trying a simple server client TCP socket in java. Server can send multiple lines as response.
I am using while((str = in.readLine())!= null) at client side and it hangs after reading the response. Please find the code below. I have searched before posting. I am making sure I am ending the response with new line.

I have tried combinations of \n, \r\n but readLine is not detecting the end of line.
But it works fine at server end.

Please help.

Thanks.

SERVER:

import java.net.*;
import java.io.*;
public class SimpleServer {
public static void main(String args[]) throws IOException {

    ServerSocket s = new ServerSocket(55555);
    Socket socket = s.accept();

    BufferedReader in = new BufferedReader(
            new InputStreamReader(socket.getInputStream()));

    PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

    String inputLine= null;
    System.out.println("call processInput"); 

       while ((inputLine = in.readLine()) != null) {
           System.out.println("before call processInput");           
           out.print("200 Success \r\n");
           out.flush();
           System.out.println("after call processInput: ");            
    }
    System.out.println("after while");
    out.close();
    in.close();
    socket.close();
    }
}

CLIENT:

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.CharBuffer;

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

          try {

              System.out.println(":Connect");
                  Socket s = new Socket("192.168.1.114",55555);
                  System.out.println("Socket:" + s); 


                  System.out.println("after :Connect");



                  OutputStream s1out = s.getOutputStream();


                  PrintWriter output = new PrintWriter(s1out, true);   
                  output.println("login user root");
                  output.flush();


                  BufferedReader in = new BufferedReader(
                        new InputStreamReader(
                            s.getInputStream()));

                  System.out.println( in.readLine());



                  output.println("servershare");
                  output.flush();
                  System.out.println( "servershare");
                  String str = null;


             while((str = in.readLine())!= null) // hangs here
             {
                  System.out.println(str);

              }


               System.out.println( "share");
               output.println("share file1.txt file1.html, roopa ramesh");
                   str = null;
                   while((str = in.readLine())!= null && !str.equals(""))
                  System.out.println(str);

                  in.close();
                  output.close();
                  s.close();







          } catch (UnknownHostException e) {

                  // TODO Auto-generated catch block

                  e.printStackTrace();

          } catch (IOException e) {

                  // TODO Auto-generated catch block

                  e.printStackTrace();

          } 
     }
}

Upvotes: 1

Views: 3926

Answers (1)

JB Nizet
JB Nizet

Reputation: 691943

You have a deadlock :

  1. client sends login
  2. server reads login line and sends 200 OK, and waits for the next line
  3. client reads 200 OK
  4. client sends servershare
  5. server reads servershare line, sends 200 OK, and waits for the next line
  6. client reads 200 OK, and waits for the next line

Both the client and the server are waiting for the next line from the other end. Your protocol isn't correct.

Moreover, you're using the platform default encoding at server-side and client-side to read and write the messages. If the client and server don't have the same default encoding, you'll have a problem. You should wrap your streams with Input/Output stream writers and specify a specific encoding when constructing them.

Upvotes: 4

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