Plz help me with Java networking

Question

I made two programs and run both of them simultaneously on two command prompts. The command prompt which runs Server code is intended to print "Yo hello" after the Client (code given) is connected to it. But I'm getting NoSuchElenentException on nextLine() method(11th line of Server code) and I don't know what's wrong with it. Any help with explanation is greatly appreciated :)
https://code.sololearn.com/ckwN4XJBvWex/?ref=app
https://code.sololearn.com/cG0nLvf9OON2/?ref=app

Answer 1

This might help you
https://www.javatpoint.com/socket-programming

Answer 2

🌀 Shail Murtaza شعیل مرتضیٰ thank you so much I found the error in my code. My code worked fine when I closed the output stream in the client code (https://www.sololearn.com/post/1403415/?ref=app pw.close() after writing message). But I don't know why I get error when I don't close it. Do you know the reason?

Answer 3

zemiak Yes I'm running server first. And I've found a lot of stuff after many trails. The message only is delivered when the output buffer from client is flushed. wow

Answer 4

You tried changing the localhost to 127.0.0.1 or InetAddress addr =
InetAddress.getByName(null/“localhost”) then pass this to client
Socket with port

https://code.sololearn.com/cqpqGo8Wc2nR/?ref=app

*change server port to 8080
**good example of sockets with explanations

https://www.nakov.com/inetjava/lectures/part-1-sockets/InetJava-1.4-TCP-Sockets.html

Answer 5

Kamen Studentov I'm not understanding what you're saying. What changes do I make?

Answer 6

I try Rishi codes on SoloLearn by thread and it works
main() is renamed to mainServer()

class Test {
public static void main(String[] args)
throws Exception {
new Thread( ()-> {
try { Server.mainServer(args); }
catch( Exception ex) {
System.err.println( ex);
}
}).start();

Client.mainClient(args);
}
}

Answer 7

Using a while loop try to make the server wait for a client to connect and if it does print the client message if it was sent.

Answer 8

zemiak
You used some lambda function and I don't know it😅 So can you give me that code without using lambda expressions plz :)

Answer 9

ok, without lambda

new Thread( new Runnable() {
public void run() {
...
}
}).start();

Answer 10

Rishi
I don't know about sockets in java.
but in C
But in I have to bind the port and IP, which you have done.
Then start listening.
Then accept a connection from client.

Edit:
And in client side I have to bind port and IP and then connect. you have just bind it.

this might help you.
and this is the same procedure of sockets in PYTHON and C++ too. I think you have to do same thing in java but not sure.

Answer 11

Rishi
I'm saying that because socket implementation of any language depends upon the operating systems. This is not language dependent. That is why I think you are missing some steps in server and client files. These are the same procedure for both Windows and Linux. Not sure about Mac. Never used it

Answer 12

🌀 Shail Murtaza شعیل مرتضیٰ zemiak Kamen Studentov

Can you find any errors in these?

https://www.sololearn.com/post/1403417/?ref=app

https://www.sololearn.com/post/1403415/?ref=app

https://www.sololearn.com/post/1403414/?ref=app

Answer 13

run server first,
how you do it ?

Answer 14

Since you are recieving data from your client the issue may be with the Scanner. Have you tried using BufferedReader instead?

Answer 15

Kamen Studentov no, I'll try that right away

Answer 16

Kamen Studentov
In the server code, the accept() method at line 9 waits until the client is connected and only then resumes the command to next line. So that's not the problem in my code