Unity 4.3.1f1 and websocket-sharp freeze Unity Editor.

Self build websocket-sharp, and add dll (Assets/Plugins). And Unity Editor freeze.

using UnityEngine;
using System.Collections;

using System;
using System.Threading;
using WebSocketSharp;

public class NewBehaviourScript : MonoBehaviour {

void Start () {

    using (WebSocket ws = new WebSocket ("ws://localhost:8080")) {

        print ("Open socket: "+ ws.ReadyState);

        print ("Websocket Alive: "+ ws.IsAlive);


        ws.OnMessage += (sender, e) => {
            print("From srv:" + e.Data);
        };

        ws.OnOpen += (sender, e) => {

            print("WebSocket-> Open:");

            print ("Open socket-> OnOpen: "+ ws.ReadyState);

        };
        ws.OnError += (sender, e) => {
            print("WebSocket-> Error:"+ e.Message);

            print ("Open socket-> OnError: "+ ws.ReadyState);
        };

        ws.OnClose += (sender, e) => {
            print("WebSocket-> Close-code:"+ e.Code);
            print("WebSocket-> Close-reason:"+ e.Reason);

            print ("Open socket-> OnClose: "+ ws.ReadyState);
        };

        ws.Connect ();
    }

}

Start by reproducing the freeze with Unity 4.3.1f1, the self-built websocket-sharp DLL in Assets/Plugins, and the supplied MonoBehaviour example. No source file or test is named, so first trace the Connect and disposal sequence in this reproduction; done means identifying the cause and verifying that the Unity Editor no longer freezes.