Ping 导致未处理的异常

Question

我有一个服务器 IP 地址列表，在我的应用程序的一部分中，在向每个服务器发送请求之前，我会对其进行 ping 操作。当我通过 VS 2012 对其进行测试时，中途停止并在 VS 中显示一个页面，显示“无法连接到远程服务器”。我在 try-catch 中有 ping，但它不属于异常部分；它只是在执行 ping.send() 时死掉。其他一些 ping 超时，我捕捉到这些并显示正确的消息。当我检查异常跟踪（如下）时，它说：“无法建立连接，因为目标机器主动拒绝它”。有什么办法可以捕捉和处理这个而不是阻止程序运行？

这是（部分）ping 码：

public static string PingServer(string host)
{
    PingOptions options = new PingOptions();
    options.DontFragment = true;
    Ping p = new Ping();
    PingReply reply = null;
    string NetworkMessage = string.Empty;

    try
    {
        string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
        byte[] buffer = Encoding.ASCII.GetBytes(data);
        int timeout = 120;
        Console.WriteLine(host);
        reply = p.Send(host, timeout, buffer, options);

这是异常跟踪：

System.Net.WebException was unhandled
  HResult=-2146233079
  Message=Unable to connect to the remote server
  Source=System
  StackTrace:
       at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
       at PASSCrawlerNS.PASSCrawler.GetResponseCallback(IAsyncResult ar) in c:\Users\blah\Documents\Visual Studio 2012\Projects\test\test\Program.cs:line 102
       at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Net.ContextAwareResult.Complete(IntPtr userToken)
       at System.Net.HttpWebRequest.SetResponse(Exception E)
       at System.Net.ConnectionReturnResult.SetResponses(ConnectionReturnResult returnResult)
       at System.Net.Connection.CompleteConnectionWrapper(Object request, Object state)
       at System.Net.PooledStream.ConnectionCallback(Object owningObject, Exception e, Socket socket, IPAddress address)
       at System.Net.ServicePoint.ConnectSocketCallback(IAsyncResult asyncResult)
       at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
       at System.Net.ContextAwareResult.Complete(IntPtr userToken)
       at System.Net.Sockets.Socket.ConnectCallback()
       at System.Threading._ThreadPoolWaitOrTimerCallback.PerformWaitOrTimerCallback(Object state, Boolean timedOut)
  InnerException: System.Net.Sockets.SocketException
       HResult=-2147467259
       **Message=No connection could be made because the target machine actively refused it** 56.245.253.10:80
       Source=System
       ErrorCode=10061
       NativeErrorCode=10061
       StackTrace:
            at System.Net.Sockets.Socket.EndConnect(IAsyncResult asyncResult)
            at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)
   InnerException: 

当我手动 ping 此服务器 (56.245.253.10) 时，它会回复。

Answer 1

如果你只是想通过ping方法测试服务器是否处于活动状态，你可以试试这个

    private async Task<bool> PingHost(string ip)
    {
        bool pingable = true;
        Ping mypinger = new Ping();
        try
        {
            PingReply reply = mypinger.Send(ip);
            pingable = (reply.Status == IPStatus.Success) ? true : false;
        }
        catch (PingException)
        {
            return false;
        }
        return pingable;
    }

它是异步运行的，所以不会阻塞你的主线程。您必须从另一个异步方法中使用 await 运算符调用它