C#ServerSocket

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using LitJson;

public class Program{
    static Socket serverSocket;
    static Socket listenScoket;
    static int byt;
    static byte[] buf;
    static byte[] bufsend;
    static string str;
    static Thread threadSend, threadRec;

    public static void Main (string[] args){
        serverSocket = new Socket (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        IPEndPoint ipEndpoint = new IPEndPoint (IPAddress.Parse ("127.0.0.1"), 3333);
        serverSocket.Bind (ipEndpoint);
        serverSocket.Listen (20);
        buf = new byte[1024];
        bufsend = new byte[1024];

        listenScoket = serverSocket.Accept ();

        if (listenScoket.Connected) {
//            threadRec = new Thread (new ThreadStart(ReceiveSocket));
//            threadRec.IsBackground = true;
//            threadRec.Start ();

            threadSend = new Thread (new ThreadStart (SendSocket));
            threadSend.IsBackground = true;
            threadSend.Start ();

        } else {
            Console.WriteLine ("fail");
        }
                
        Console.ReadKey ();
    }

    public static void SendSocket(){
        while (true) {
//            string userid = Console.ReadLine ();
//            string state = Console.ReadLine ();
//            string sends = "{\"userid\":\"" + userid + "\",\"state\":\"" + state + "\"}";
            string sends = "{\"server\":\"00\"}";
            bufsend = Encoding.UTF8.GetBytes (sends);
            listenScoket.Send (bufsend);
        }
    }
        
    public static void ReceiveSocket(){
        while(true){
            byt = listenScoket.Receive(buf);
            if(byt>0){
                str = Encoding.UTF8.GetString(buf);
                Console.WriteLine(str);

                bufsend = Encoding.UTF8.GetBytes ("{\"userid\":\"id123\",\"state\":\"03\"}");
                listenScoket.Send (bufsend);
            }
        }
    }
}