[Unity] Client is not receiving message from server.

In Unity 2018.2.16f, I'm trying to create both server and client in the editor.
I'm running the server code first:

IEnumerator ServerInit()
{
	var wssv = new WebSocketServer ("ws://127.0.0.1:9528");
	wssv.AddWebSocketService<Laputa> ("/Laputa");
	wssv.Start ();
	yield return 0;
}

public class Laputa : WebSocketBehavior
{
	protected override void OnMessage (MessageEventArgs e)
	{
		var msg = e.Data == "BALUS"
			? "I've been balused already..."
			: "I'm not available now.";

		Send (msg);
	}
}

After few seconds I'm executing the client code:

IEnumerator ClientCoroutine()
{
	using (var ws = new WebSocket("ws://127.0.0.1:9528/Laputa"))
	{
		ws.OnMessage += (sender, e) =>
			print("Laputa says: " + e.Data);

		ws.Connect();
		ws.Send("BALUS");
	}
	yield return 0;
}

But there is not message is receiving. There is no error either. Looks like nothing is happening. What am I missing?

Start by reproducing the server and client coroutines in Unity 2018.2.16f with websocket-sharp, then trace the WebSocket Connect, Send, and OnMessage flow shown in the issue. Done means identifying why the server response is not received and confirming the client prints the reply or documenting the missing setup.