flutter connection to java using sockets

I have a server that has been implemented by java and a flutter code and I want to connect this two by sockets in both sides. but the flutter side does not connect to java.how can I do this?
here is my simplified code for flutter side:

import 'dart:io';
import 'dart:async';

void main() async{
    Socket socket = await Socket.connect("10.0.2.2",8080);
    print('the work has finished');
    socket.write("hello");
    print('ok');
}

this is the java endpoint implementation:

public class main {
    public static void main(String[] args) {
        Server server = new Server();
        try(Socket socket = server.serverSocket.accept(); DataInputStream dataInputStream = new DataInputStream(socket.getInputStream())){
            System.out.println("someone has connected to this device");
            String message = dataInputStream.readUTF();
            System.out.println(message);
        }catch(Exception e){
            System.out.println(e.getMessage());
        }
    }
}

it is good to mention that the server class in used in java side just listens on a specified port =.