1.

使用 System.Net.Sockets API 创建一个套接字并连接到服务器。为了清楚起见，System.Net.Sockets API 的调用被封装在 SocketClient 类中。

定义头（使用 _socket 变量存储 Socket 对象。_clientDone 变量是一个 ManualResetEvent，用于协调通过Sockets API 调用的异步调用）：

// Cached Socket object that will be used by each call for the lifetime of this class        Socket _socket = null;        // Signaling object used to notify when an asynchronous operation is completed        static ManualResetEvent _clientDone = new ManualResetEvent(false);        // Define a timeout in milliseconds for each asynchronous call. If a response is not received within this         // timeout period, the call is aborted.        const int TIMEOUT_MILLISECONDS = 5000;        // The maximum size of the data buffer to use with the asynchronous socket methods        const int MAX_BUFFER_SIZE = 2048;

在 SocketClient.cs 中，添加以下方法，该方法将创建 TCP 套接字，并向服务器发送异步连接请求。此操作的响应将由内联回调进行处理

public string Connect(string hostName, int portNumber)        {            string result = string.Empty;            DnsEndPoint hostEntry = new DnsEndPoint(hostName, portNumber);            _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);                        // Create a SocketAsyncEventArgs object to be used in the connection request            SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();            socketEventArg.RemoteEndPoint = hostEntry;            socketEventArg.Completed += new EventHandler
     
      (delegate(object s, SocketAsyncEventArgs e)            {
                    result = e.SocketError.ToString();                _clientDone.Set();            });            _clientDone.Reset();            _socket.ConnectAsync(socketEventArg);             _clientDone.WaitOne(TIMEOUT_MILLISECONDS);            return result;        }
     

 

2.

public string Send(string data)        {            string response = "Operation Timeout";            // We are re-using the _socket object that was initialized in the Connect method            if (_socket != null)            {                // Create SocketAsyncEventArgs context object                SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();                // Set properties on context object                socketEventArg.RemoteEndPoint = _socket.RemoteEndPoint;                socketEventArg.UserToken = null;                // Inline event handler for the Completed event.                // Note: This event handler was implemented inline in order to make this method self-contained.                socketEventArg.Completed += new EventHandler
     
      (delegate(object s, SocketAsyncEventArgs e)                {                    response = e.SocketError.ToString();                    // Unblock the UI thread                    _clientDone.Set();                });                // Add the data to be sent into the buffer                byte[] payload = Encoding.UTF8.GetBytes(data);                socketEventArg.SetBuffer(payload, 0, payload.Length);                // Sets the state of the event to nonsignaled, causing threads to block                _clientDone.Reset();                // Make an asynchronous Send request over the socket                _socket.SendAsync(socketEventArg);                // Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.                // If no response comes back within this time then proceed                _clientDone.WaitOne(TIMEOUT_MILLISECONDS);            }            else            {                response = "Socket is not initialized";            }            return response;        }
     

3.

public string Receive()        {            string response = "Operation Timeout";            // We are receiving over an established socket connection            if (_socket != null)            {                // Create SocketAsyncEventArgs context object                SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();                socketEventArg.RemoteEndPoint = _socket.RemoteEndPoint;                // Setup the buffer to receive the data                socketEventArg.SetBuffer(new Byte[MAX_BUFFER_SIZE], 0, MAX_BUFFER_SIZE);                // Inline event handler for the Completed event.                // Note: This even handler was implemented inline in order to make this method self-contained.                socketEventArg.Completed += new EventHandler
     
      (delegate(object s, SocketAsyncEventArgs e)                {                    if (e.SocketError == SocketError.Success)                    {                        // Retrieve the data from the buffer                        response = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);                        response = response.Trim('\0');                    }                    else                    {                        response = e.SocketError.ToString();                    }                    _clientDone.Set();                });                // Sets the state of the event to nonsignaled, causing threads to block                _clientDone.Reset();                // Make an asynchronous Receive request over the socket                _socket.ReceiveAsync(socketEventArg);                // Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.                // If no response comes back within this time then proceed                _clientDone.WaitOne(TIMEOUT_MILLISECONDS);            }            else            {                response = "Socket is not initialized";            }            return response;        }        /// 
      
        /// Closes the Socket connection and releases all associated resources        /// 
        public void Close()        {            if (_socket != null)            {                _socket.Close();            }        }