Speed up Port Scan C#

Question

I am trying to create port scanner in C#, so far I have this:

private void ip()
{
    int start = 70;
    int end = 80;
    string ipString;
    if (this.comboBox1.Text == "Domain") {
         ipString= Dns.GetHostEntry(txtHost.Text).AddressList[0].ToString();
    }
    else {
        ipString = txtHost.Text;
    }
    TcpClient asd = new TcpClient();
    // MessageBox.Show(ipString);     
    IPAddress address = IPAddress.Parse(ipString);
    for (int i = start; i <= end; i++)
    {
        try
        {
            asd.SendTimeout = 3000;
            asd.ReceiveTimeout = 3000;
            asd.Connect(address, i);

            if (asd.Connected)
            {
                MessageBox.Show("Port " + i + " is open");
            }
        }
        catch
        {
            MessageBox.Show("Port " + i + " is closed");
        }
    }
}

However for closed ports, it's kinda slow, around 20 seconds, what should I do to make the process faster? Thanks a lot.

"it's kinda slow". You should measure which bit is slow so we don't have to guess. — spender, Nov 25 '12 at 14:03
Maybe related: http://stackoverflow.com/questions/1331902/c-sharp-tcp-port-scanner-resources — rene, Nov 25 '12 at 14:04
You should consider the async networking APIs. There are many to choose from, but if you value your sanity, consider .net4.5 and the async/await apis. Also worth considering that none of the .net DNS apis are any good. Perhaps a 3rd party option might be considered. See: http://stackoverflow.com/questions/11480742/dns-begingethost-methods-blocking — spender, Nov 25 '12 at 14:07

score 1 · Answer 1 · answered Nov 25 '12 at 14:03

1

You should use threading.

http://msdn.microsoft.com/en-us/library/aa645740(v=vs.71).aspx

Fire up separate thread for every port you want to check and let the callbacks inform you which of them is open and which is not.

answered Nov 25 '12 at 14:03

Igor Perić

171
1
8

1

How can I call thread with multiple parameters ? private void ip(strin ip, int start, int end) { } ? – user1815324 Nov 25 '12 at 14:04
3

How can you suggest this when you don't even know which part is "kinda slow"? Adding extra threads is rarely a good answer to speeding up networking code. – spender Nov 25 '12 at 14:05
1

Threading is going to be needed in any case since his code would block the main UI thread no matter what he did. Networking code needs threading. – Igor Perić Nov 25 '12 at 14:17
@IgorPerić Not necessarily, there are quite capable async methods in TcpClient too. – Joachim Isaksson Nov 25 '12 at 15:51

score 0 · Answer 2 · edited Jan 08 '14 at 11:35

0

You should have your delegate and async function declared like this (two parameters in example)

public delegate void UpdateUIThreadDelegate(int par1, int par2);
void UpdateUIThread(int par1, int par2)
{
       ...
}

And you should call you async function like this:

this.Invoke(new UpdateUIThreadDelegate(UpdateUIThread), new object[] { par1, par2 });

edited Jan 08 '14 at 11:35

BenMorel

34,448
50
182
322

answered Nov 25 '12 at 14:13

Igor Perić

171
1
8

score 0 · Answer 3 · edited Dec 08 '13 at 03:40

0

You need to close the connection after you are done testing it.

try asd.Close(); at the end of your catch statement.

It sped up the process for me significantly.

edited Dec 08 '13 at 03:40

Andre Silva

4,782
9
52
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answered Dec 08 '13 at 03:03

1nd1g0111

1

Speed up Port Scan C#

3 Answers3