Thread: an't get acknowledgement message from server side when image is received from client

Hello Guys !
Firstly please forgive my ignorance. Below is my simple code for client and server. Client simply sends an image to server and server reads the image and saves it. Server sends an acknowledgement message to client when image is saved. The PROBLEM is client never reads/gets the acknowledgement message. Below is my code for client and server.
Any help would be appreciated. Thank you

Client code :

import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.net.Socket;
import javax.imageio.ImageIO;
 
 
public class clientImageSender {
    public static void main(String[] args) {
        Socket sock=null;
        BufferedImage image=null;
        String serverMessage;
        InputStreamReader isReader;
        BufferedReader bReader;
        try{
           sock=new Socket("127.0.0.1",4444);
           while((image=ImageIO.read(new File("clientImage.jpg")))!=null)
           {
              ImageIO.write(image, "jpg", sock.getOutputStream());
              System.out.println("Image sent");
 
           }//below code never runs 
          isReader=new InputStreamReader(sock.getInputStream());// gets acknoledgement by server when image is received on server's side
          bReader = new BufferedReader(isReader);
          serverMessage=bReader.readLine();
          System.out.println(serverMessage);
 
          System.out.println("This code is running");
 
        }//try block
        catch(Exception e){
            e.printStackTrace();
        }
 
    }
    }

Server code :
Java Code:

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import javax.imageio.ImageIO;
 
 
public class ServerImageReceiver {
    public static void main(String[] args) {
 
 
        try
        {
            ServerSocket serverSocket=new ServerSocket(4444);
            System.out.println("server is running");
           while(true)
           {
               System.out.println("Server is waiting for connection");
               try
               { 
                Socket sock=serverSocket.accept();
                System.out.println("Connected");
 
                BufferedImage image;
                while((image=ImageIO.read(sock.getInputStream()))!=null)
                {
                ImageIO.write(image, "jpg",new File("newImage.jpg"));
                System.out.println("Image saved");
                }
 
 
                //sending acknowledgement message to client
                PrintWriter sendMe=new PrintWriter(sock.getOutputStream());
                sendMe.println("File Received:Message by server");
                sendMe.flush();
                System.out.println("Server side message sent");
 
               }
               catch(Exception e)
               {
                   e.printStackTrace();
 
               }
 
            }
        }
       catch(Exception e)
       {
           e.printStackTrace();
       }
    }
 
}

Originally Posted by java_monster

The PROBLEM is client never reads/gets the acknowledgement message.

So the question is, "Why not?"
Follow the flow and see where things seem to go unexpected.
Does the server actually connect with the client? Does the image get sent?...somewhere along the path things are not what was expected.

Originally Posted by jps

So the question is, "Why not?"
Follow the flow and see where things seem to go unexpected.
Does the server actually connect with the client? Does the image get sent?...somewhere along the path things are not what was expected.

Firstly that you for the response .
Yes the server connects and receives the image successfully. But the problem is the Client side never receives server's message " File Received:Message by server ". I cannot figure out where the flow actually gets stuck and the code which receives server's message on the client side never runs.

Please help . . . . .

Add some more printlns to see exactly which line of code is the last one to be executed as expected

java_monster,
Do you know the behavior of loops? I believe yes.
Do you know the behavior of reading from sockets and reading from files? I believe no.
In your client code you are having a while loop that reads from a file. As long as the file exists it will always return image and its never null.
So you are able to sent the image to server. On the server side you again have loop. The loop will not finish until the client socket is closed.
So you are not going beyond the loops on both the sides.
Just remove the loops and try.

Syed.

Originally Posted by syedbhai

java_monster,
Do you know the behavior of loops? I believe yes.
Do you know the behavior of reading from sockets and reading from files? I believe no.
In your client code you are having a while loop that reads from a file. As long as the file exists it will always return image and its never null.
So you are able to sent the image to server. On the server side you again have loop. The loop will not finish until the client socket is closed.
So you are not going beyond the loops on both the sides.
Just remove the loops and try.

Syed.

Shah saheb thank you for you comment. I removed the loops and the problem is still not solved.Now the client sends the image but server never receives it . Can you please edit my code and post a working code here ? And will you please suggest me good source/website/ebook to follow.

Originally Posted by java_monster

Can you please edit my code and post a working code here ?

We discourage people providing working code solutions on this forum, please do not encourage people to do so. Please see this post and this post on getting help

Originally Posted by java_monster

I removed the loops and the problem is still not solved

Have you followed the suggestions in post 2 and 4? What were the results? What questions do you have remaining?

Hello.
You made a mistake.
Please remove that additional loop in the client as well.
And remove the inner while loop on the server side.
Again, don't keep any loop in the client code. And don't keep inner loop in the server code.
The code shall work.
let me know.

Syed.

JPS I am sorry I didn't know the rules of the forum.
JPS and SyedBhai I followed your suggestions now the server never receives the image , although client gets successfully connected. Is it possible ImageIO.write() on client side sends more data than ImageIO.read() on server side can read?

Below is my edited code according to suggestions and output of programs on both server and client side.

Client code:
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.net.Socket;
import javax.imageio.ImageIO;
 
 
public class clientImageSender {
    public static void main(String[] args) {
        Socket sock=null;
        BufferedImage image=null;
        String serverMessage;
        InputStreamReader isReader;
        BufferedReader bReader;
        try{
           sock=new Socket("127.0.0.1",4444);
 
              image=ImageIO.read(new File("clientImage.jpg"));
              ImageIO.write(image, "jpg", sock.getOutputStream());
              System.out.println("Image sent");
              System.out.println("Receiving server's message");//but it never recives
          isReader=new InputStreamReader(sock.getInputStream());// gets acknoledgement by server when      //image is received on server's side
          bReader = new BufferedReader(isReader);
          serverMessage=bReader.readLine();
          System.out.println(serverMessage);
          System.out.println("This code is running");
 
 
        }//try block
        catch(Exception e){
            e.printStackTrace();
        }
 
 
    }
    }

Server Code :
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import javax.imageio.ImageIO;
 
 
public class ServerImageReceiver {
    public static void main(String[] args) {
 
 
        try
        {
            ServerSocket serverSocket=new ServerSocket(4444);
            System.out.println("server is running");
            BufferedImage image;
 
               System.out.println("Server is waiting for connection");
               while(true)
           {
                Socket sock=serverSocket.accept();
                System.out.println("Connected to client mechine");
                image=ImageIO.read(sock.getInputStream());
                ImageIO.write(image, "jpg",new File("newImage.jpg"));
                System.out.println("Image saved");
                PrintWriter sendMe=new PrintWriter(sock.getOutputStream());
                sendMe.println("File Received:Message by server");
                sendMe.flush();
                System.out.println("Server side message sent");
 
 
 
            }
        }
       catch(Exception e)
       {
           e.printStackTrace();
       }
    }
 
}

Client's output:
image sent
Receiving server's message

Server's output:
server is running
Server is waiting for connection
Connected to client mechine

Originally Posted by java_monster

Is it possible ImageIO.write() on client side sends more data than ImageIO.read() on server side can read?

Interesting theory. You could send a small picture, a single pixel, and see if that works.

According to the given output the server gets to here:

System.out.println("Connected to client mechine");
image=ImageIO.read(sock.getInputStream());
ImageIO.write(image, "jpg",new File("newImage.jpg"));
System.out.println("Image saved");

...you could add another println, as there are two lines of code in question, to determine if the upper line executes or not.
..same for the client, try to narrow down what happens and what does not.

Hello.
Can you try sending some sample string first instead of an image?
If everything works fine then the problem could be with ImageIO.

syed.

Originally Posted by syedbhai

Hello.
Can you try sending some sample string first instead of an image?
If everything works fine then the problem could be with ImageIO.

syed.

Yes it can send and received text without any problem.

--- Update ---

Originally Posted by jps

Interesting theory. You could send a small picture, a single pixel, and see if that works.

According to the given output the server gets to here:

System.out.println("Connected to client mechine");
image=ImageIO.read(sock.getInputStream());
ImageIO.write(image, "jpg",new File("newImage.jpg"));
System.out.println("Image saved");

...you could add another println, as there are two lines of code in question, to determine if the upper line executes or not.
..same for the client, try to narrow down what happens and what does not.

I tried sending small picture...... still the same problem. I tried your second suggestion , this line seems to block further processing by server side I don't know why

image=ImageIO.read(sock.getInputStream());

Hello.
Can you just try sending and receiving of an image as a one complete byte array? You can skip ImageIO API.
If things work okay then you can work on ImageIO API.

Syed.

Hello SyedBhai ! Yes that seems to be only option. Thank you so much for your help. Also I thank JPS for responses.
Regards !
Aka Peeruk