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UDP Port Scanner

Posted on 2003-11-14
Medium Priority
Last Modified: 2012-05-04
Could someone show me how to make a UDP port scanner in delphi.

I've aready made a TCP port scanner, but how would I make a UDP port scanner.

Could someone show me how this is done?
Question by:Shinez
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Accepted Solution

GloomyFriar earned 400 total points
ID: 9750481
Just open UDP socket instead TCP socket ;-)

Author Comment

ID: 9751204
How Would I do this?

Expert Comment

ID: 9753785
Ok, I'll try to explain.
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Expert Comment

ID: 9753825
It's impossible to scan UDP port if it just was opened.
You can determine that UDP port is opened by sending some datagram to the port only.
And if you'll be lucky you'll got an answer from the server.
But server is not obliged to answer to you if you don't know its protocol ;-)

So, if you know what server you are looking for and you know its protocol then try to send some command (according to the protocol) and wait for an answer from the server. ip-by-ip, port-by-port ;-)

Good luck.

Author Comment

ID: 9758218
could you show me how this is done, have edit1 for ip and edit2 for port and for label1 to display if port is open/close.

if I wanted to check if the port is open for ut2003.

default game port is 7777, the query port is 7778.

how would I get a responce that the server is up?

please could you give some code with your answer, I don't know that much about UDP.


Expert Comment

ID: 9762835
There is no "open" and "close" terms applying to the UDP protocol.

Var buff: array[0..256] of byte;
   UDPClient := TNMUDP.Create(self);
   UDPClient.RemoteHost := 'ut2003'; // or something like ''
   UDPClient.RemotePort := 7778;
   UDPClient.LocalPort := 7777;
   UDPClient.OnDataReceived := UDPClientDataReceived;
   UDPClient.OnStatus := UDPClientStatus;
   UDPClient.OnInvalidHost := UDPClientInvalidHost;
   UDPClient.OnStreamInvalid := UDPClientStreamInvalid;
   UDPClient.OnBufferInvalid := UDPClientBufferInvalid;

   StrPCopy(buff, "Hello!");
   try UDPClient.SendBuffer(buff, 7);
     // Error

procedure TMainForm.UDPClientDataReceived(Sender: TComponent;
  NumberBytes: Integer; FromIP: String);
Var buff: array[0..256] of byte;
  UDPClient.ReadBuffer(buff, NumberBytes);


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