TcpClient.Connect函数连接超时的问题

问题原述：

http://topic.youkuaiyun.com/t/20060616/15/4825920.html

 

调用TcpClient.Connect函数连接其他机器。我在一台机器上测试程序，对于连接根本无法连接（物理连接不通）的机器，该函数用时5秒左右返回，并捕获SocketException异常。我在另一台机器上测试时，Connect函数用时26秒左右的时间才返回。请问有没有方法设置Connect函数连接超时的时间，如果超过一定时间还没有连上则返回。

 

解决方法：

   写了个帮助类，用了线程池   
    
class TcpClientConnector { /// <summary> /// 在指定时间内尝试连接指定主机上的指定端口。 /// </summary> /// <param name="hostname">要连接到的远程主机的 DNS 名。</param> /// <param name="port">要连接到的远程主机的端口号。</param> /// <param name="millisecondsTimeout">要等待的毫秒数，或 -1 表示无限期等待。</param> /// <returns>已连接的一个 TcpClient 实例。</returns> /// <remarks>本方法可能抛出的异常与 TcpClient 的构造函数重载之一 /// public TcpClient(string, int) 相同，并若指定的等待时间是个负数且不等于 /// -1，将会抛出 ArgumentOutOfRangeException。</remarks> public static TcpClient Connect(string hostname, int port, int millisecondsTimeout) { ConnectorState cs = new ConnectorState(); cs.Hostname = hostname; cs.Port = port; ThreadPool.QueueUserWorkItem(new WaitCallback(ConnectThreaded), cs); if (cs.Completed.WaitOne(millisecondsTimeout, false)) { if (cs.TcpClient != null) return cs.TcpClient; throw cs.Exception; } else { cs.Abort(); throw new SocketException(11001); // cannot connect } } private static void ConnectThreaded(object state) { ConnectorState cs = (ConnectorState)state; cs.Thread = Thread.CurrentThread; try { TcpClient tc = new TcpClient(cs.Hostname, cs.Port); if (cs.Aborted) { try { tc.GetStream().Close(); } catch { } try { tc.Close(); } catch { } } else { cs.TcpClient = tc; cs.Completed.Set(); } } catch (Exception e) { cs.Exception = e; cs.Completed.Set(); } } private class ConnectorState { public string Hostname; public int Port; public volatile Thread Thread; public readonly ManualResetEvent Completed = new ManualResetEvent(false); public volatile TcpClient TcpClient; public volatile Exception Exception; public volatile bool Aborted; public void Abort() { if (Aborted != true) { Aborted = true; try { Thread.Abort(); } catch { } } } } }      
 

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  用法示例：   
   
try { Console.WriteLine("Connecting to nonexistenthost..."); TcpClient tc = TcpClientConnector.Connect("nonexistent", 80, 1000); Console.WriteLine("Returned"); try { tc.GetStream().Close(); } catch { } try { tc.Close(); } catch { } } catch (Exception e) { Console.WriteLine("Exception: " + e.Message); }