ClientWebSocket支持Win7和.net45

namespace TestApp
{
    class Program
    {
        
        const string WSS_TEST_SERVER = "wss://echo.websocket.org";

        static void Main(string[] args)
        { 
            TestConnection(WSS_TEST_SERVER).GetAwaiter().GetResult();
        }
static async Task TestConnection(string server)
        {
            using (var ws = new System.Net.WebSockets.Managed.ClientWebSocket())
            {
                //建立连接 
                await ws.ConnectAsync(new Uri(server), CancellationToken.None);
                const string msg = "";
                var testMsg = new ArraySegment<byte>(Encoding.UTF8.GetBytes(msg));
                // 没必要传值的话可以注释掉，直接用接收的方法
                //await ws.SendAsync(testMsg, WebSocketMessageType.Text, true, CancellationToken.None);
                while (true)
                {
                    var buffer = new ArraySegment<byte>(new byte[1024]);
                    var read = await ws.ReceiveAsync(buffer, CancellationToken.None);
                    var replyMsg = Encoding.UTF8.GetString(buffer.Array, 0, read.Count); 
                }
            } 
        }
    }
}