检查与本地服务器的连接：等待时间的端口

Question

我正在尝试创建一个函数来测试与 server:port 的连接，它将尝试每 100 毫秒连接到该 server:port 并返回 TRUE 如果连接成功则返回 FALSE 直到达到时间限制。 我的功能如下：

private static bool _TryPing(string strIpAddress, int intPort, int nTimeoutMsec)
        {
            Socket socket = null;
            try
            {
                socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, false);  
                IAsyncResult result = socket.BeginConnect(strIpAddress, intPort, null, null);
                bool success = result.AsyncWaitHandle.WaitOne(nTimeoutMsec, true);

                return socket.Connected;
            }
            catch
            {
                return false;
            }
            finally
            {
                if (null != socket)
                    socket.Close();
            }
        }

问题是我正在使用另一个软件来制作本地服务器：端口，并且需要随机 10-20 秒才能完成新端口的设置。但是上面的函数会在应用程序启动时检查，所以它会立即返回 false 而无需等待，因为 port 尚未打开。

_TryPing("127.0.0.1", 1080, 20000) //Return FALSE

谁能帮我修复这段代码。谢谢

Answer 1

如果端口未打开，则连接将立即失败。如果你想等待一段时间看看端口是否打开，你需要在循环中重试连接，直到连接成功或超时，例如：

private static bool hasElapsed(ref Stopwatch sw, int total)
{
    return (sw.ElapsedMilliseconds > (long) total);
}

private static bool hasElapsed(ref Stopwatch sw, int total, out int remaining)
{
    remaining = (int) (((long) total) - sw.ElapsedMilliseconds);
    return (remaining < 0);
}

private static bool _TryPing(string strIpAddress, int intPort, int nTimeoutMsec)
{
    Stopwatch sw = Stopwatch.StartNew();
    do
    {
        try
        {
            using (TcpClient tcp = new TcpClient())
            {
                tcp.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, true);
                IAsyncResult ar = tcp.BeginConnect(strIpAddress, intPort, null, null);
                WaitHandle wh = ar.AsyncWaitHandle;
                try
                {
                    int remaining;
                    if (!hasElapsed(ref sw, nTimeoutMsec, out remaining))
                    {
                        if (wh.WaitOne(remaining))
                        {
                            tcp.EndConnect(ar);
                            return true;
                        }
                    }
                    tcp.Close(); 
                }
                finally
                {
                    wh.Close();
                }
            }
        }
        catch
        {
        }
    }
    while (!hasElapsed(sw, nTimeoutMsec));
    return false;
}

Answer 2

试试这个，我不知道为什么，但我需要将 WaitTime 除以 3 以使此功能正常运行...

private static bool TryConnect(string IP, int Port, int WaitTime)
        {
            int RunEvery = 500;
            for (int i = 0; i <= WaitTime/3; i += RunEvery)
            {
                TcpClient client = new TcpClient();
                try
                {
                    client.Connect(IP, Port);
                    Console.WriteLine(IP + ":" + Port + " is active");
                    return true;
                }
                catch(SocketException e)
                {
                    Console.WriteLine("Connection could not be established due to: \n" + e.Message);                    
                    Thread.Sleep(RunEvery);
                }
                finally
                {
                    client.Close();
                }
            }
            return false;
        }