用async与await 写socket客户端！！！

[taz01]

刚刚接触socket 看了软件官方 的demo 太多代码，就想用重新写一次
参考了好多资料，最终代码如下：
运行一次是正确有，但运行多次的时候 就会出错。
求大神指点一下

class Program
    {
        static void Main(string[] args)
        {
            var cmd = "add 1 2 4" + Environment.NewLine;
            Task.Run(async delegate { await SocketExts.SendAsync(cmd); });
            Task.Run(async delegate { await SocketExts.SendAsync(cmd); });
            Task.Run(async delegate { await SocketExts.SendAsync("ECHO this is a test" 
                                       + Environment.NewLine); });
            Task.WaitAll(Task.Delay(2000));
        }
    }

public static class SocketExts
    {
        public async static Task<string> SendAsync(string msg,
                               string ip = "127.0.0.1", int port = 2012)
        {
            using (var client = new Socket(AddressFamily.InterNetwork, 
                                          SocketType.Stream, ProtocolType.Tcp))
            {
                var remoteEP = new IPEndPoint(IPAddress.Parse(ip), port);
                await Task.Factory.FromAsync(client.BeginConnect,
                                                  client.EndConnect, remoteEP, null);

                byte[] byteData = Encoding.ASCII.GetBytes(msg);
                var result = client.BeginSend(byteData, 0, byteData.Length, 0,
                                                                       _ => { }, client);
                await Task.Factory.FromAsync(result, (r) => client.EndSend(r));

                StateObject state = new StateObject();
                state.workSocket = client;
                var received = client.BeginReceive(state.buffer, 0,
                                StateObject.BufferSize, 0,
                                                       _ => { }, state);
                var response = await Task<string>.Factory.FromAsync(received, ar =>
                {
                    ReceiveCallback(ar);
                    return ((StateObject)ar.AsyncState).sb.ToString();
                });


                Console.WriteLine("=======Response received : {0}=====", response);
                client.Shutdown(SocketShutdown.Both);
                client.Close();
                return response;
            }
        }
        private static void ReceiveCallback(IAsyncResult ar)
        {
            StateObject state = (StateObject)ar.AsyncState;
            Socket client = state.workSocket;
            int bytesRead = client.EndReceive(ar);
            if (bytesRead > 0)
            {
                state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));
                client.BeginReceive(state.buffer, 0, bytesRead, SocketFlags.None, 
                                       new AsyncCallback(ReceiveCallback), client);
            }
        }
    }

    public class StateObject
    {
        public Socket workSocket = null;
        public const int BufferSize = 1024;
        public byte[] buffer = new byte[BufferSize];
        public StringBuilder sb = new StringBuilder();
    }

[以专业开发人员为伍]

在.net中，尽量不要使用Socket。它不是基于IOCP的，它是用来一些人移植java代码用的。应该使用TcpListner和TcpClient，这样才能在并发量大时获得性能提升。 你的代码有太多的需要修改的地方了，实在是难以一一指出（太累了）。最为重要的一点，比如说tcp是会自动平衡网络带宽的，因此有着粘包和分包的结果，而你的代码 state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead)); 则完全不考虑分包的情况。 我曾经贴过一个 Tcp 长连接的“底层”的例子（没有包括信令的业务处理部分）：http://bbs.csdn.net/topics/390987992 虽然在信令上比你的这个短链接的稍微复杂（2、3条语句），但是还是可以参考一下。里边对于许多必须考虑到的底层的东西都基本上有所演示。