java socket : message not getting transferred

[thorny blade]

Hi All,

[neon sandal]

<@&987246399047479336> please have a look, thanks.

[neon sandal]

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[thorny blade]

i am having issue in setting up the clietn

[neon sandal]

I uploaded your attachments as gist. That way, they are easier to read for everyone, especially mobile users 👍

[shy pendant]

What's your question?

[thorny blade]

i'm supposed to send messages via socket

i open 2 remote servers and done this

but message is not getting copied

this is how it should be ideally

this is what i'm getting

[sweet egret]

Try flushing your output right after writing it

[shy pendant]

ServerSocket cannot be non-blocking, it always blocks

In your example, you have both apps bind to port 28220. But only 1 thing can be bound to a port on a single network card at a time

So it seems like there's a few problems with your code, unless you're testing on completely different machines

[thorny blade]

both of them are different remote servers

so it is fine

[shy pendant]

Oh alright. So do you know which line it's halting at?

[thorny blade]

so , i tried debugging

after forming the connections

after creating the input , outstreams, if i print anything , it is not showing on console

  try {
                System.out.println( "TCP connection established..." );
                ObjectInputStream input = new ObjectInputStream(client.getInputStream());
                ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
                System.out.println("input and output stream formed ");
                output.writeObject( message + " from " +
                                    InetAddress.getLocalHost( ).getHostName( ) );
                System.out.println( ( String )input.readObject( ) );
                System.out.println("message delivered  ");
            } catch ( Exception e ) {
                error( e );
            }

[neon sandal]

Detected code, here are some useful tools:

Formatted code

try {
  System.out.println("TCP connection established...");
  ObjectInputStream input = new ObjectInputStream(client.getInputStream());
  ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
  System.out.println("input and output stream formed ");
  output.writeObject(message + " from " + InetAddress.getLocalHost().getHostName());
  System.out.println((String) input.readObject());
  System.out.println("message delivered  ");
} catch (Exception e) {
  error(e);
}

[thorny blade]

the lines , input and output stream formed, are not running

neither does the message delivered one

[shy pendant]

But there are other print statements that should have printed before "TCP connection established", right?

Such as "connection accepted"

[thorny blade]

yes, you are right

[shy pendant]

So why is your output going right to "TCP connection established"?

[thorny blade]

i actually

[neon sandal]

I uploaded your attachments as gist. That way, they are easier to read for everyone, especially mobile users 👍

[shy pendant]

Oh alright

[thorny blade]

i was trying to debug earlier, since no success, i started on a fresh file

[shy pendant]

So, Object streams use header data to establish a connection

ObjectInputStream is waiting for the header data

You should create the output stream first, which sends the header data, then create the input stream

Start by fixing that

[thorny blade]

i did that

still no change

                System.out.println( "TCP connection established..." );
                ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
                
              
                output.writeObject( message + " from " +
                                    InetAddress.getLocalHost( ).getHostName( ) );
                ObjectInputStream input = new ObjectInputStream(client.getInputStream()); 
                System.out.println( ( String )input.readObject( ) );
                System.out.println("message delivered  ");
            } catch ( Exception e ) {
                error( e );
            }

[thorny blade]

i did that , it didn't work

[shy pendant]

It's not going to fix your entire app, but it should get you to the next print statement

Seems like the connection is being established, but it was failing at the streams. To fix the stream part, you need to create the output before the input

Don't even send data before both output & input have been established

It's hard to help when you keep changing the code

[thorny blade]

apologies for that

[neon sandal]

I uploaded your attachments as gist. That way, they are easier to read for everyone, especially mobile users 👍

[thorny blade]

this is the code as of now

[shy pendant]

Alright, and what are the results as of now?

[thorny blade]

i get tcp connection only

i'm just changing this function in try catch

                System.out.println( "TCP connection established..." );
                ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
                System.out.println("output");
                ObjectInputStream input = new ObjectInputStream(client.getInputStream()); 
                System.out.println("input ");
                output.writeObject( message + " from " +
                                    InetAddress.getLocalHost( ).getHostName( ) );
               
                System.out.println( ( String )input.readObject( ) );
                System.out.println("message delivered  ");
            } catch ( Exception e ) {
                error( e );
            }```

[neon sandal]

Detected code, here are some useful tools:

Formatted code

try {
  System.out.println("TCP connection established...");
  ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
  System.out.println("output");
  ObjectInputStream input = new ObjectInputStream(client.getInputStream());
  System.out.println("input ");
  output.writeObject(message + " from " + InetAddress.getLocalHost().getHostName());
  System.out.println((String) input.readObject());
  System.out.println("message delivered  ");
} catch (Exception e) {
  error(e);
}

[thorny blade]

it stops at ouput

i am not sure why input stream is not getting formed

[shy pendant]

Where did "output" come from? Is that the message you're sending?

Cause I don't see a println("output") in your code

[shy pendant]

Oh, here

Are you sure both apps are using the most recent code?

[thorny blade]

yes

[thorny blade]

tthe message i'm sending is the 3rd argument on both the machines

[shy pendant]

Well, the endpoints established a connection just fine, or else the output stream would not have created properly

And you create the input stream right after the output stream

So if the code you're showing really is the most updated code, I don't see an issue

[shy pendant]

Could you post the full code one more time? Seems like you made a change between the last file upload and thid

[shy pendant]

The full code

[thorny blade]

this is what my batchmate have done, exact same code , but she is getting the output

[shy pendant]

Well wait, now you remove "output" and "input"

You keep changing the code....

[thorny blade]

here's my full code

[neon sandal]

I uploaded your attachments as gist. That way, they are easier to read for everyone, especially mobile users 👍

[thorny blade]

this is not mine, this is of my batchmate, i asked for reference because our code exactly same but my input stream is not getting created

[thorny blade]

this is mine

[shy pendant]

In your code, you accepted a connection using accept(), but then you do nothing with it

That's a bit suspicious

Does your mate do that too?

[thorny blade]

yes, once the server accepts the connection

when we run this code on the 2 machines, 1 machine becomes the server and the other becomes client

we are initializing both of them in the constructor

https://stackoverflow.com/questions/22361951/java-can´t-get-objectinputstream-from-socket

i came across this now

[shy pendant]

That's what I said here

What I'm saying is, server.accept() returns a Socket. But you ignore the accepted socket in your code

You don't assign it to a variable

Notice in the SO question how they do java Socket socket = serverSocket.accept();

But you just do java serverSocket.accept();

[thorny blade]

not able to figure it out

i'll probably update you tomorrow if anything works

[shy pendant]

It sounds like you have 2 apps, let's call em App1 and App2. They're supposed to communicate.

App1 creates a server. App2 connects to the server. That is 1 established connection

But then App2 establishes a server, which App1 connects to

So you are basically establishing 2 connections between the apps, instead of 1 connection

I believe that's why you're getting confused

[thorny blade]

i have a single application this which i'm running from 2 different machines ( passed in arguments)
when i run both of them , one takes the role of client and the other the role of server,

output stream is formed first

the code blocks at input stream , i'm trying to figure out why

i've tried add output.flush() in the end

but no success so far

[shy pendant]

It's the same app, I'm saying 2 apps because they are different instances of the same app

So you have the app which runs on machine 1 (App1) and the app which runs on machine 2 (App2)

And you should have 1 connection between them, right?

But you are actually establishing 2 connections between them

The first when App1 connects to App2's ServerSocket

The second when App2 connects to App1's ServerSocket

[sweet egret]

Have you tried running the app twice, on the same machine, with localhost and a different port per applicatie

[thorny blade]

it should have been client = server.accept() ;

i got confused with the way variable was defined,

thanks for your help really appreciate it

[shy pendant]

Yup

No problem

[neon sandal]

Closed the thread.