I am new to Dart Development and I am having a problem about concurrency. I am trying to understand Socket.io. I followed the Socket.io tutorial on its website and now trying to build my code in Dart.

I implemented these 2 files

server.dart

import "package:socket_io/socket_io.dart";

void main(List<String> args) {
  Server io = Server();

  io.on("connect", (client) {
    print("Connection occurred");

    client.on("msg", (data) {
      print("Message received: $data");
    });
  });

  io.listen(3000);
  print("Socket IO server running on port 3000");
}

client.dart

import 'dart:io';

import 'package:socket_io_client/socket_io_client.dart' as IO;

Future<void> main() async {
  // Dart client
  IO.Socket socket = IO.io('http://localhost:3000', <String, dynamic>{
    'transports': ['websocket'],
    'autoConnect': false,
  });

  socket.connect();

  for(int a = 0; a < 4; a++){
    String? name = stdin.readLineSync();
    if(name! == "add"){
      socket.emit("msg", "A MESSAGE");
    }
  }
}

pubsec.yaml dependencies

dependencies:
  flutter:
    sdk: flutter
  
  web_socket_channel: ^2.1.0
  
  cupertino_icons: ^1.0.6
  ansicolor: ^2.0.2
  socket_io_client: ^1.0.0
  socket_io: ^1.0.1
  flutter_js: ^0.8.1

I first start the server.dart and then client.dart. In the client.dart my expectation is whenever I type add in the terminal I will receive **message received: A MESSAGE ** immediately. Instead program waits for the end of the for loop and the prints **message received: A MESSAGE ** on the server terminal. Why this is happening.

I think for loop blocks the whole flow of the client program but I already connected the server with socket.connect. But i did not understand why it is blocking.