How can I receive UDP packets into Unity Webplayer?

I am building a simple webplayer that accept remote user input. However, I can’t seem to send anything into it. The programs below compiles file and run fine, but will not receive anything. I tried port 1023 - 25000, no avail. I am running this from Unity Editor. I use free UDP Test tool to send message to 127.0.0.1. When I re-do this code for a C# console application, it works well. But not from Unity Webplayer build. Could someone help?

using UnityEngine;
using System.Collections;

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Text;

public class UDPDemo : MonoBehaviour {
	
	private UdpClient receivingUdpClient;	
	private IPEndPoint remoteIpEndPoint;

	private Thread thread;
	
	// port number
	private int receivePort = 843;
	
	// Use this for initialization
	void Start () {
		try {
			receivingUdpClient = new UdpClient(receivePort);
		} catch (Exception e) {
			Debug.Log (e.ToString());
		}
		
		remoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);

		// start the thread for receiving signals
		thread = new Thread(new ThreadStart(ReceiveDataBytes));
		thread.Start();
		
		// debug
		Debug.Log("Thread started");
	}
	
   	
	void ReceiveDataBytes() {
		while (true) {
			Debug.Log ("Threading inside while");
			// NOTE!: This blocks execution until a new message is received
			Byte[] receivedBytes = receivingUdpClient.Receive(ref remoteIpEndPoint);
			String receivedStringData = Encoding.ASCII.GetString(receivedBytes);
			Debug.Log ("I received : " + receivedStringData);
			Debug.Log ("The message was sent from " + remoteIpEndPoint.Address.ToString() + " on port number " + remoteIpEndPoint.Port.ToString());

			Thread.Sleep(8);
		}
	}
	

	void CloseClient() {
		thread.Abort();
		receivingUdpClient.Close();
	}
	
	void OnApplicationQuit() {
		CloseClient();
	}
}

Finally! I’ll answer my own question again. After googling and digging into Unity forum, documentation (see here, and here, see how it begins with “In Unity 3.0…”) and Answer website (see this and this one too), I found the answer!
I come to a conclusion that the answer (at the moment) is …

NOT POSSIBLE

…but there are workarounds, such as this one.