1.串連到 TCP 通訊端伺服器
使用 System.Net.Sockets API 建立一個通訊端並串連到伺服器。為了清楚起見,System.Net.Sockets API 的調用被封裝在 SocketClient 類中。
定義頭(使用 _socket 變數儲存 Socket 對象。_clientDone 變數是一個 ManualResetEvent,用於協調通過Sockets API 呼叫的非同步呼叫):
// 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,該方法將建立 TCP 通訊端,並向伺服器發送非同步串連請求。此操作的響應將由內聯回調進行處理
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<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e) { result = e.SocketError.ToString(); _clientDone.Set(); }); _clientDone.Reset(); _socket.ConnectAsync(socketEventArg);
_clientDone.WaitOne(TIMEOUT_MILLISECONDS); return result; }
2.向 TCP 通訊端伺服器發送資料
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<SocketAsyncEventArgs>(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.接收來自 TCP 通訊端伺服器的資料
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<SocketAsyncEventArgs>(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; } /// <summary> /// Closes the Socket connection and releases all associated resources /// </summary> public void Close() { if (_socket != null) { _socket.Close(); } }