如何在C#中进行非阻塞套接字调用以确定连接状态？

Question

Socket上Connected属性的MSDN文档说明如下:

Connected属性的值反映了最近操作时的连接状态.如果需要确定连接的当前状态,请进行非阻塞,零字节发送调用.如果调用成功返回或抛出WAEWOULDBLOCK错误代码(10035),则套接字仍然连接; 否则,套接字不再连接.

我需要确定连接的当前状态 - 如何进行非阻塞,零字节发送调用？

Answer 1

Socket.Connected属性(至少.NET 3.5版本)的MSDN文档底部的示例显示了如何执行此操作:

// .Connect throws an exception if unsuccessful
client.Connect(anEndPoint);

// This is how you can determine whether a socket is still connected.
bool blockingState = client.Blocking;
try
{
    byte [] tmp = new byte[1];

    client.Blocking = false;
    client.Send(tmp, 0, 0);
    Console.WriteLine("Connected!");
}
catch (SocketException e) 
{
    // 10035 == WSAEWOULDBLOCK
    if (e.NativeErrorCode.Equals(10035))
        Console.WriteLine("Still Connected, but the Send would block");
    else
    {
        Console.WriteLine("Disconnected: error code {0}!", e.NativeErrorCode);
    }
}
finally
{
    client.Blocking = blockingState;
}

 Console.WriteLine("Connected: {0}", client.Connected);