Win7 No PingCompletedCallback on timeout?

[Gavin Coates]

Hey guys, I wrote a network scanning tool a few years ago, which pings a list of IP addresses. I recently moved to Windows 7, and have noticed some strange behaviour in the program. My ping code is as follows:

public void pingIP(int IP)
{
AutoResetEvent waiter = new AutoResetEvent (false);
string IPaddress = IPpart1.Value.ToString() + "." + IPpart2.Value.ToString() + "." + IPpart3.Value.ToString() + "." + IP;
IPAddress IPa = IPAddress.Parse(IPaddress);

        Debug.WriteLine("Pinging " + IP.ToString());
        
        Ping ping = new Ping();
        ping.PingCompleted += new PingCompletedEventHandler(PingCompletedCallback);

        ping.SendAsync(IPa, waiter);
        
    }

This then calls PingCompletedCallback when it recieves a response:

public void PingCompletedCallback(object sender, PingCompletedEventArgs e)
{

        PingReply reply = e.Reply;
            // get the IP that was pinged
            string IP = reply.Address.ToString();
            
            if(IP != "0.0.0.0")
            {
                string\[\] IParray = IP.Split('.');
                int iIP = Int32.Parse(IParray\[3\]);
                if (reply.Status == IPStatus.Success)
                    pingResult\[iIP\] = reply.RoundtripTime.ToString();
                else
                    pingResult\[iIP\] = "X";
            
                Debug.WriteLine("Ping Reply From " + IP.ToString() + " Time: " + pingResult\[iIP\]);

                // check if the last ping (255) has been reveived and mark the ping complete flag if so
                if (iIP == 255)
                {
                    pingComplete = true;
                    lblStatus.Text = "Ping Complete";
                }
            }
            
            
            
        ((AutoResetEvent)e.UserState).Set();
    }

Now, under Windows XP this worked fine, PingCompletedCallback was called for every ping I sent - either with a response, or with a timeout. I could then set the value as required. However, under Win7, PingCompletedCallback only seems to be called when a successful response is received. I have also noticed I recieve a lot of replies from "0.0.0.0", as well as multiple replies from the IP the machine is running on (10.0.0.4) I have a second screen for doing a detailed ping on a single IP, which doesnt use a call