【.Net】Socket小示例

引言

项目中用到了Socket，这里做个控制台小示例记录一下。

Client

客户端的Receive用了异步方法，保持长连接，可以随时发送消息和响应服务端的消息，如下

        static string ClientReceiveMessage = "";
        static byte[] receivedBytes = new byte[];
        static void Main(string[] args)
        {

            IPHostEntry ipHost = Dns.Resolve("127.0.0.1");
            IPAddress ipAddress = ipHost.AddressList[];
            IPEndPoint ipEndPoint = new IPEndPoint(ipAddress, );

            string sendingMessage = "Hello World Socket Test";

            Console.WriteLine("Creating message: Hello World Socket Test");

            Socket sender = new Socket(AddressFamily.InterNetwork,
                                   SocketType.Stream,
                                   ProtocolType.Tcp);
            sender.Connect(ipEndPoint);

            sender.BeginReceive(receivedBytes, , receivedBytes.Length, , ReceiveCallback, sender);

            while (true)
            {
                sendingMessage = Console.ReadLine();
                byte[] forwardMessage = Encoding.ASCII.GetBytes(sendingMessage + "[FINAL]");
                sender.Send(forwardMessage);
            }
        }

        private static void ReceiveCallback(IAsyncResult ar)
        {
            Socket client = (Socket)ar.AsyncState;

            int totalBytesReceived = client.EndReceive(ar);

            if (totalBytesReceived > )
            {

                ClientReceiveMessage += Encoding.ASCII.GetString(receivedBytes, , totalBytesReceived);
               if (ClientReceiveMessage.IndexOf("[FINAL]", StringComparison.Ordinal) > -)
                {
                    Console.WriteLine(ClientReceiveMessage);
                    ClientReceiveMessage = "";
                }   

                client.BeginReceive(receivedBytes, , receivedBytes.Length, , new AsyncCallback(ReceiveCallback), client);
            }
            else
            {
                Console.WriteLine("服务端结束不再发送消息！" );
                ClientReceiveMessage = "";
            }

        }

Server

服务端循环异步Accept，可以接收多个client消息，并且马上回复。

        static ManualResetEvent allDone = new ManualResetEvent(false);
        static void Main(string[] args)
        {

            Socket listener = new Socket(AddressFamily.InterNetwork,
                                         SocketType.Stream,
                                         ProtocolType.Tcp);
            listener.Bind(new IPEndPoint(IPAddress.Any, ));
            listener.Listen();

            while (true)
            {
                allDone.Reset();
                listener.BeginAccept(ar =>
            {
                allDone.Set();

                Socket MyServer = (Socket)ar.AsyncState;

                Socket service = MyServer.EndAccept(ar);

                byte[] receivedBytes = new byte[];

                while (true)
                {
                    string receivedValue = string.Empty;
                    int numBytes = service.Receive(receivedBytes);
                    receivedValue += Encoding.ASCII.GetString(receivedBytes,, numBytes);

                    if (receivedValue.IndexOf("[FINAL]", StringComparison.Ordinal) > -)
                    {
                        Console.WriteLine("Received value: {0} from " + service.RemoteEndPoint, receivedValue);
                        string replyValue = "Message successfully received.[FINAL]";
                        byte[] replyMessage = Encoding.ASCII.GetBytes(replyValue);
                        service.Send(replyMessage);
                    }
                }
              }, listener);

                allDone.WaitOne();
            }

注意事项

1.Socket的Receive方法响应次数，是以缓冲数组的大小划分。如果数组大小为1024，消息为2048，Receive将会触发两次。作为接收方无法通过Receive来确定是否已完整接收，所以要对消息另作处理，例如在消息中增加[FINAL]来确定消息已发送完毕。

2.如果没有消息发送，接收方Receive方法会一直等待。但如果发送方调用Shutdown(SocketShutdown.Send)方法，接收方的Receive会马上返回0，所以在非来回传递消息的情况下，可以Shutdown方法来实现消息发送完毕。

3.可以设置ReceiveTimeout的值，超时会抛出异常，然而只能作用于Receive方法，对BeginReceive无效。