c# – System.Net.Sockets.SocketException创建websocket连接时

using System;
using WebSocketSharp;


namespace WebsocketTest
{
    class Program
    {
        public static void Main(string[] args)
        {
            try
            { 
            using (var ws = new WebSocketSharp.WebSocket("ws://192.168.18.186:7884"))
            {
               Console.WriteLine("started");
                ws.Connect();
                ws.Send("START");
                Console.ReadLine();
                }
            }catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadLine();
            }

        }
    }
}

但是我无法创建与在另一台机器上运行的websocket服务器的连接.我收到这样的错误信息

09-05-2017 16:20:41|Fatal|WebSocket.connect:0|System.Net.Sockets.SocketException (0x80004005): No connection could be made because the target machine actively refused it 192.168.18.186:7884
                             at System.Net.Sockets.TcpClient..ctor(String hostname,Int32 port)
                             at WebSocketSharp.WebSocket.setClientStream()
                             at WebSocketSharp.WebSocket.doHandshake()
                             at WebSocketSharp.WebSocket.connect()

与我的代码有关的问题是什么？有什么好的websocket库可用吗？