Question

Question: I want to search the subnet for all computers in it.
So I send a ping to all IP addresses in the subnet.

The problem is it works fine if I only scan 192.168.0.“.
But if I scan 192.168..*”, then I get an “Out of memory” exception.

Why ? Do I have to limit the threads, or is the problem the memory consumed by new ping which doesn’t get destructed once finished, or do I need to call gc.collect() ?

    static void Main(string[] args)
    { 
        string strFromIP = "192.168.0.1";
        string strToIP = "192.168.255.255";

        Oyster.Math.IntX omiFromIP = 0;
        Oyster.Math.IntX omiToIP = 0;
        IsValidIP(strFromIP, ref omiFromIP);
        IsValidIP(strToIP, ref omiToIP);
        for (Oyster.Math.IntX omiThisIP = omiFromIP; omiThisIP <= omiToIP; ++omiThisIP)
        {
            Console.WriteLine(IPn2IPv4(omiThisIP));
            System.Net.IPAddress sniIPaddress = System.Net.IPAddress.Parse(IPn2IPv4(omiThisIP));
            SendPingAsync(sniIPaddress);
        }

        Console.WriteLine(" --- Press any key to continue --- ");
        Console.ReadKey();
    } // Main


    // http://pberblog.com/post/2009/07/21/Multithreaded-ping-sweeping-in-VBnet.aspx
    // http://www.cyberciti.biz/faq/how-can-ipv6-address-used-with-webbrowser/#comments
    // http://www.kloth.net/services/iplocate.php
    // http://bytes.com/topic/php/answers/829679-convert-ipv4-ipv6
    // http://stackoverflow.com/questions/1434342/ping-class-sendasync-help
    public static void SendPingAsync(System.Net.IPAddress sniIPaddress)
    {
        int iTimeout = 5000;
        System.Net.NetworkInformation.Ping myPing = new System.Net.NetworkInformation.Ping();
        System.Net.NetworkInformation.PingOptions parmPing = new System.Net.NetworkInformation.PingOptions();

        System.Threading.AutoResetEvent waiter = new System.Threading.AutoResetEvent(false);
        myPing.PingCompleted += new System.Net.NetworkInformation.PingCompletedEventHandler(AsyncPingCompleted);
        string data = "ABC";
        byte[] dataBuffer = Encoding.ASCII.GetBytes(data);

        parmPing.DontFragment = true;
        parmPing.Ttl = 32;

        myPing.SendAsync(sniIPaddress, iTimeout, dataBuffer, parmPing, waiter);
        //waiter.WaitOne();
    }


    private static void AsyncPingCompleted(Object sender, System.Net.NetworkInformation.PingCompletedEventArgs e)
    {

        System.Net.NetworkInformation.PingReply reply = e.Reply;
        ((System.Threading.AutoResetEvent)e.UserState).Set();
        if (reply.Status == System.Net.NetworkInformation.IPStatus.Success)
        {
            Console.WriteLine("Address: {0}", reply.Address.ToString());
            Console.WriteLine("Roundtrip time: {0}", reply.RoundtripTime);
        }
    }

Answer 1

Finally… No ping requried at all…

http://www.codeproject.com/KB/cs/c__ip_scanner.aspx

All I needed to do is to make it thread-safe for debugging.
Changing Add to:

void Add( string m )
{
    Invoke(new MethodInvoker(
        delegate
        {
            add.Items.Add(m);
        }));
    //add.Items.Add( m );
}

 

Private Sub Add(m As String)
    Invoke(New MethodInvoker(Function() Do
        add.Items.Add(m)
    End Function))
    'add.Items.Add(m);'
End Sub