C#之Socket斷線重連

一、網上常用方法

1、當Socket.Conneted == false時，調用如下函數進行判斷

 

/// /// 當socket.connected為false時，進一步確定下當前連接狀態 /// /// private bool IsSocketConnected() { #region remarks /********************************************************************************************  * 當Socket.Conneted為false時， 如果您需要確定連接的當前狀態，請進行非阻塞、零字節的 Send 調用。  * 如果該調用成功返回或引發 WAEWOULDBLOCK 錯誤代碼 (10035)，則該套接字仍然處於連接狀態；  * 否則，該套接字不再處於連接狀態。  * Depending on http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.connected.aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2  ********************************************************************************************/ #endregion #region 過程 // This is how you can determine whether a socket is still connected. bool connectState = true; bool blockingState = socket.Blocking; try { byte[] tmp = new byte[1]; socket.Blocking = false; socket.Send(tmp, 0, 0); //Console.WriteLine("Connected!"); connectState = true; //若Send錯誤會跳去執行catch體，而不會執行其try體里其之后的代碼 } catch (SocketException e) { // 10035 == WSAEWOULDBLOCK if (e.NativeErrorCode.Equals(10035)) { //Console.WriteLine("Still Connected, but the Send would block"); connectState = true; } else { //Console.WriteLine("Disconnected: error code {0}!", e.NativeErrorCode); connectState = false; } } finally { socket.Blocking = blockingState; } //Console.WriteLine("Connected: {0}", client.Connected); return connectState; #endregion }

2、根據socket.poll判斷

 

 

/// /// 另一種判斷connected的方法，但未檢測對端網線斷開或ungraceful的情況 /// /// /// static bool IsSocketConnected(Socket s) { #region remarks /* As zendar wrote, it is nice to use the Socket.Poll and Socket.Available, but you need to take into conside ration  * that the socket might not have been initialized in the first place.  * This is the last (I believe) piece of information and it is supplied by the Socket.Connected property.  * The revised version of the method would looks something like this:  * from：http://stackoverflow.com/questions/2661764/how-to-check-if-a-socket-is-connected-disconnected-in-c */ #endregion #region 過程 return !((s.Poll(1000, SelectMode.SelectRead) && (s.Available == 0)) || !s.Connected); /* The long, but simpler-to-understand version: bool part1 = s.Poll(1000, SelectMode.SelectRead); bool part2 = (s.Available == 0); if ((part1 && part2 ) || !s.Connected) return false; else return true; */ #endregion }

 

 

總結：

1、此兩種方法出處可在函數體中的remark中找到鏈接

2、此兩種方法適用於對端正常關閉socket下的本地socket狀態檢測，在非正常關閉如

   斷電、拔網線的情況下不起作用因為Socket.Conneted存在bug，詳見.Net Bugs

 

二、支持物理斷線重連功能的類

    利用BeginReceive + KeepAlive實現物理斷線重連，初步測驗了一下，正常。(部分

代碼參考帖子#26及blog在C#中利用keep-alive處理socket網絡異常斷開)

    Keep-Alive機制的介紹請看TCP Keepalive HOWTO，以此備忘，同時希望能幫助到

有需要的同學。

 

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Net.Sockets; using System.Net; using System.Threading; namespace MySocket { public class Socket_wrapper { //委托 private delegate void delSocketDataArrival(byte[] data); static delSocketDataArrival socketDataArrival = socketDataArrivalHandler; private delegate void delSocketDisconnected(); static delSocketDisconnected socketDisconnected = socketDisconnectedHandler; public static Socket theSocket = null; private static string remoteHost = "192.168.1.71"; private static int remotePort = 6666; private static String SockErrorStr = null; private static ManualResetEvent TimeoutObject = new ManualResetEvent(false); private static Boolean IsconnectSuccess = false; //異步連接情況，由異步連接回調函數置位 private static object lockObj_IsConnectSuccess = new object(); /// /// 構造函數 /// /// /// public Socket_wrapper(string strIp, int iPort) { remoteHost = strIp; remotePort = iPort; } /// /// 設置心跳 /// private static void SetXinTiao() { //byte[] inValue = new byte[] { 1, 0, 0, 0, 0x20, 0x4e, 0, 0, 0xd0, 0x07, 0, 0 };// 首次探測時間20 秒, 間隔偵測時間2 秒 byte[] inValue = new byte[] { 1, 0, 0, 0, 0x88, 0x13, 0, 0, 0xd0, 0x07, 0, 0 };// 首次探測時間5 秒, 間隔偵測時間2 秒 theSocket.IOControl(IOControlCode.KeepAliveValues, inValue, null); } /// /// 創建套接字+異步連接函數 /// /// private static bool socket_create_connect() { IPAddress ipAddress = IPAddress.Parse(remoteHost); IPEndPoint remoteEP = new IPEndPoint(ipAddress, remotePort); theSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); theSocket.SendTimeout = 1000; SetXinTiao();//設置心跳參數 #region 異步連接代碼 TimeoutObject.Reset(); //復位timeout事件 try { theSocket.BeginConnect(remoteEP, connectedCallback, theSocket); } catch (Exception err) { SockErrorStr = err.ToString(); return false; } if (TimeoutObject.WaitOne(10000, false))//直到timeout，或者TimeoutObject.set() { if (IsconnectSuccess) { return true; } else { return false; } } else { SockErrorStr = "Time Out"; return false; } #endregion } /// /// 同步receive函數 /// /// /// public string socket_receive(byte[] readBuffer) { try { if (theSocket == null) { socket_create_connect(); } else if (!theSocket.Connected) { if (!IsSocketConnected()) Reconnect(); } int bytesRec = theSocket.Receive(readBuffer); if (bytesRec == 0) { //warning 0 bytes received } return Encoding.ASCII.GetString(readBuffer, 0, bytesRec); } catch (SocketException se) { //print se.ErrorCode throw; } } /// /// 同步send函數 /// /// /// public bool socket_send(string sendMessage) { if (checkSocketState()) { return SendData(sendMessage); } return false; } /// /// 斷線重連函數 /// /// private static bool Reconnect() { //關閉socket theSocket.Shutdown(SocketShutdown.Both); theSocket.Disconnect(true); IsconnectSuccess = false; theSocket.Close(); //創建socket return socket_create_connect(); } /// /// 當socket.connected為false時，進一步確定下當前連接狀態 /// /// private bool IsSocketConnected() { #region remarks /********************************************************************************************  * 當Socket.Conneted為false時， 如果您需要確定連接的當前狀態，請進行非阻塞、零字節的 Send 調用。  * 如果該調用成功返回或引發 WAEWOULDBLOCK 錯誤代碼 (10035)，則該套接字仍然處於連接狀態；  * 否則，該套接字不再處於連接狀態。  * Depending on http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.connected.aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2  ********************************************************************************************/ #endregion #region 過程 // This is how you can determine whether a socket is still connected. bool connectState = true; bool blockingState = theSocket.Blocking; try { byte[] tmp = new byte[1]; theSocket.Blocking = false; theSocket.Send(tmp, 0, 0); //Console.WriteLine("Connected!"); connectState = true; //若Send錯誤會跳去執行catch體，而不會執行其try體里其之后的代碼 } catch (SocketException e) { // 10035 == WSAEWOULDBLOCK if (e.NativeErrorCode.Equals(10035)) { //Console.WriteLine("Still Connected, but the Send would block"); connectState = true; } else { //Console.WriteLine("Disconnected: error code {0}!", e.NativeErrorCode); connectState = false; } } finally { theSocket.Blocking = blockingState; } //Console.WriteLine("Connected: {0}", client.Connected); return connectState; #endregion } /// /// 另一種判斷connected的方法，但未檢測對端網線斷開或ungraceful的情況 /// /// /// public static bool IsSocketConnected(Socket s) { #region remarks /* As zendar wrote, it is nice to use the Socket.Poll and Socket.Available, but you need to take into consideration * that the socket might not have been initialized in the first place. * This is the last (I believe) piece of information and it is supplied by the Socket.Connected property. * The revised version of the method would looks something like this: * from：http://stackoverflow.com/questions/2661764/how-to-check-if-a-socket-is-connected-disconnected-in-c */ #endregion #region 過程 if (s == null) return false; return !((s.Poll(1000, SelectMode.SelectRead) && (s.Available == 0)) || !s.Connected); /* The long, but simpler-to-understand version: bool part1 = s.Poll(1000, SelectMode.SelectRead); bool part2 = (s.Available == 0); if ((part1 && part2 ) || !s.Connected) return false; else return true; */ #endregion } /// /// 異步連接回調函數 /// /// static void connectedCallback(IAsyncResult iar) { #region <remarks> /// 1、置位IsconnectSuccess #endregion </remarks> lock (lockObj_IsConnectSuccess) { Socket client = (Socket)iar.AsyncState; try { client.EndConnect(iar); IsconnectSuccess = true; StartKeepAlive(); //開始KeppAlive檢測 } catch (Exception e) { //Console.WriteLine(e.ToString()); SockErrorStr = e.ToString(); IsconnectSuccess = false; } finally { TimeoutObject.Set(); } } } /// /// 開始KeepAlive檢測函數 /// private static void StartKeepAlive() { theSocket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(OnReceiveCallback), theSocket); } /// /// BeginReceive回調函數 /// static byte[] buffer = new byte[1024]; private static void OnReceiveCallback(IAsyncResult ar) { try { Socket peerSock = (Socket)ar.AsyncState; int BytesRead = peerSock.EndReceive(ar); if (BytesRead > 0) { byte[] tmp = new byte[BytesRead]; Array.ConstrainedCopy(buffer, 0, tmp, 0, BytesRead); if (socketDataArrival != null) { socketDataArrival(tmp); } } else//對端gracefully關閉一個連接 { if (theSocket.Connected)//上次socket的狀態 { if (socketDisconnected != null) { //1-重連 socketDisconnected(); //2-退出，不再執行BeginReceive return; } } } //此處buffer似乎要清空--待實現 zq theSocket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(OnReceiveCallback), theSocket); } catch (Exception ex) { if (socketDisconnected != null) { socketDisconnected(); //Keepalive檢測網線斷開引發的異常在這里捕獲 return; } } } /// /// 異步收到消息處理器 /// /// private static void socketDataArrivalHandler(byte[] data) { } /// /// socket由於連接中斷(軟/硬中斷)的后續工作處理器 /// private static void socketDisconnectedHandler() { Reconnect(); } /// /// 檢測socket的狀態 /// /// public static bool checkSocketState() { try { if (theSocket == null) { return socket_create_connect(); } else if (IsconnectSuccess) { return true; } else//已創建套接字，但未connected { #region 異步連接代碼 TimeoutObject.Reset(); //復位timeout事件 try { IPAddress ipAddress = IPAddress.Parse(remoteHost); IPEndPoint remoteEP = new IPEndPoint(ipAddress, remotePort); theSocket.BeginConnect(remoteEP, connectedCallback, theSocket); SetXinTiao();//設置心跳參數 } catch (Exception err) { SockErrorStr = err.ToString(); return false; } if (TimeoutObject.WaitOne(2000, false))//直到timeout，或者TimeoutObject.set() { if (IsconnectSuccess) { return true; } else { return false; } } else { SockErrorStr = "Time Out"; return false; } #endregion } } catch (SocketException se) { SockErrorStr = se.ToString(); return false; } } /// /// 同步發送 /// /// /// public static bool SendData(string dataStr) { bool result = false; if (dataStr == null || dataStr.Length < 0) return result; try { byte[] cmd = Encoding.Default.GetBytes(dataStr); int n = theSocket.Send(cmd); if (n < 1) result = false; } catch (Exception ee) { SockErrorStr = ee.ToString(); result = false; } return result; } } }

轉自 https://blog.csdn.net/thebestleo/article/details/52354126