不斷檢查互聯網連接

Question

如何在我的應用程序中不斷檢查互聯網連接，並在連接不可用時作出響應？

目前我使用：

while(true) { 
if(HasConnection()) { 
    //doSomething.. 
    } 
    //stop app by 1sec 
} 

，但它似乎相當不雅。

Answer 1

如果您有Internet連接，您將如何知道？你可以將數據包路由到附近的路由器就足夠了嗎？也許機器只有一個網卡，一個網關，並且可能該網關的連接斷開，但機器仍然可以路由到網關和本地網絡？

也許機器有一個NIC和十幾個網關;也許他們一直來去，但其中一個他們總是起來？

如果機器有多個NIC，但只有一個網關會怎麼樣？也許它可以路由到互聯網的一些子集，但仍然與本地網絡沒有連接到Internet的良好連接？

如果機器具有多個網卡，多個網關，但出於管理策略的原因，只有部分互聯網是可路由的呢？

你真的只關心客戶是否連接到你的服務器？

數據包之間有什麼樣的延遲是可以接受的？ （30ms是好的，300ms正在推動人體耐力的極限，3000ms是無法忍受的長時間，960000ms是連接太陽能探測器所需要的。）什麼樣的數據包丟失是可以接受的？

你在做什麼真的試圖測量？

Answer 2

This將是一個開始，但作爲sarnold提到有很多你需要考慮

Answer 3

你正在尋找的東西NetworkAvailabilityChanged event。

要檢查互聯網連接，你可以ping一個可靠的網站，如Google.com。

請注意，每隔互聯網連接（如ISP中斷）的更改都不可能被通知。

Answer 4

超級用戶對this question的接受答案描述了Windows確定其是否具有網絡訪問權的方式。你可以使用類似的方法，但是當你的應用程序啓動時，我會產生一個單獨的線程來負責檢查。讓單獨的線程以您認爲最好的方式執行檢查，並在連接狀態更改時提出事件。

Answer 5

您可以通過ping到一些網站，例如測試互聯網連接：

public bool IsConnectedToInternet 
    { 
     try 
     { 
      using (System.Net.NetworkInformation.Ping ping = new System.Net.NetworkInformation.Ping()) 
      { 
       string address = @"http://www.google.com";//      System.Net.NetworkInformation.PingReply pingReplay = ping.Send(address);//you can specify timeout. 
       if (pingReplay.Status == System.Net.NetworkInformation.IPStatus.Success) 
       { 
        return true; 
       } 
      } 
     } 
     catch 
     { 
#if DEBUG 
      System.Diagnostics.Debugger.Break(); 
#endif//DEBUG 
     } 

     return false; 
    } 

Answer 6

如果你只需要知道，如果至少一個連接可用，你可以試試這個：

InternetGetConnectedStateEx（）

http://msdn.microsoft.com/en-us/library/aa384705%28v=vs.85%29.aspx

Answer 7

使用下面的代碼：

public static class LocalSystemConnection 
{ 
    [DllImport("wininet.dll", SetLastError=true, CallingConvention = CallingConvention.ThisCall)] 
    extern static bool InternetGetConnectedState(out ConnectionStates lpdwFlags, long dwReserved); 

    /// <summary> 
    /// Retrieves the connected state of the local system. 
    /// </summary> 
    /// <param name="connectionStates">A <see cref="ConnectionStates"/> value that receives the connection description.</param> 
    /// <returns> 
    /// A return value of true indicates that either the modem connection is active, or a LAN connection is active and a proxy is properly configured for the LAN. 
    /// A return value of false indicates that neither the modem nor the LAN is connected. 
    /// If false is returned, the <see cref="ConnectionStates.Configured"/> flag may be set to indicate that autodial is configured to "always dial" but is not currently active. 
    /// If autodial is not configured, the function returns false. 
    /// </returns> 
    public static bool IsConnectedToInternet(out ConnectionStates connectionStates) 
    { 
     connectionStates = ConnectionStates.Unknown; 
     return InternetGetConnectedState(out connectionStates, 0); 
    } 

    /// <summary> 
    /// Retrieves the connected state of the local system. 
    /// </summary> 
    /// <returns> 
    /// A return value of true indicates that either the modem connection is active, or a LAN connection is active and a proxy is properly configured for the LAN. 
    /// A return value of false indicates that neither the modem nor the LAN is connected. 
    /// If false is returned, the <see cref="ConnectionStates.Configured"/> flag may be set to indicate that autodial is configured to "always dial" but is not currently active. 
    /// If autodial is not configured, the function returns false. 
    /// </returns> 
    public static bool IsConnectedToInternet() 
    { 
     ConnectionStates state = ConnectionStates.Unknown; 
     return IsConnectedToInternet(out state); 
    } 
} 

[Flags] 
public enum ConnectionStates 
{ 
    /// <summary> 
    /// Unknown state. 
    /// </summary> 
    Unknown = 0, 

    /// <summary> 
    /// Local system uses a modem to connect to the Internet. 
    /// </summary> 
    Modem = 0x1, 

    /// <summary> 
    /// Local system uses a local area network to connect to the Internet. 
    /// </summary> 
    LAN = 0x2, 

    /// <summary> 
    /// Local system uses a proxy server to connect to the Internet. 
    /// </summary> 
    Proxy = 0x4, 

    /// <summary> 
    /// Local system has RAS (Remote Access Services) installed. 
    /// </summary> 
    RasInstalled = 0x10, 

    /// <summary> 
    /// Local system is in offline mode. 
    /// </summary> 
    Offline = 0x20, 

    /// <summary> 
    /// Local system has a valid connection to the Internet, but it might or might not be currently connected. 
    /// </summary> 
    Configured = 0x40, 
}