get all open ports from given ip address

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How to list out all open ports of the system from C#3.0.It should fast

I am trying by this code but it is very slow

C#

for (int CurrPort = 1; CurrPort <= 25; CurrPort++) 
{ 
  TcpClient TcpScan = new TcpClient(); 
  try 
  { 
    // Try to connect 
    TcpScan.Connect("192.168.0.1", CurrPort); 
    // If there's no exception, we can say the port is open 
    MessageBox.Show("Port " + CurrPort + " open"); 
  } 
  catch 
  { 
    // An exception occured, thus the port is probably closed 
    MessageBox.Show("Port " + CurrPort + " closed"); 
  }
}

Posted 10-Aug-12 7:53am

Gajendra Yadav

Updated 10-Aug-12 8:28am

Wes Aday

v2

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Comments

Philip Stuyck 10-Aug-12 13:56pm

TCP or UDP ?

Gajendra Yadav 10-Aug-12 14:13pm

Both protocol

[no name] 10-Aug-12 14:09pm

What is the problem? What have you tried? Where is the code that demonstrates your problem?

Gajendra Yadav 10-Aug-12 14:23pm

I am trying by this code but it is very slow
for (int CurrPort = 1; CurrPort <= 25; CurrPort++)

{

TcpClient TcpScan = new TcpClient();

try

{

// Try to connect

TcpScan.Connect("192.168.0.1", CurrPort);

// If there's no exception, we can say the port is open

MessageBox.Show("Port " + CurrPort + " open");

}

catch

{

// An exception occured, thus the port is probably closed

MessageBox.Show("Port " + CurrPort + " closed");

}

}

[no name] 10-Aug-12 14:30pm

Define "slow". How did you measure the time? How many iterations did you measure? How fast do you think it should be? Did you profile your code?

Gajendra Yadav 10-Aug-12 14:38pm

I tried to scan from port o to 20000 in my windows application. it is taking to much time more than 20 minutes . how to make fast.

lewax00 10-Aug-12 14:46pm

For starters, don't open a message box for every single port, save a list of open ports and just give the results at the end. Second, if possible, only create TcpScan once, outside the loop (might not work, but if it does allow for it it should be faster than creating a new one in every iteration).

StianSandberg 10-Aug-12 20:56pm

I don't think that would speed it up. Creating a TcpClient takes maybe a millisecond

lewax00 10-Aug-12 21:06pm

Still, if you were to repeat that for all ~65000 ports that's more than a minute saved. It adds up.

StianSandberg 10-Aug-12 21:21pm

20000 ports - 20 seconds of 20 minutes. That's 1/60 of the total time....

[no name] 10-Aug-12 14:50pm

So in other words, you did not measure the time and you did not profile it. Connect blocks until it connects or it fails. Checking all of the ports will take time.... a lot of time. If performance is an issue, then profile the code to find out where your bottlenecks are. Reduce the timeout on the connect so it fails faster, get a faster network, try rewriting your port sniffer in C++.

StianSandberg 10-Aug-12 21:00pm

That's 1000 pr minute! Almost 17 pr second. What did you expect?

Philip Stuyck 10-Aug-12 15:18pm

Why would you need this functionality in your C# code. There exist already port scanners ?

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Mehdi Gholam · Accepted Answer · 2012-08-10T20:33:00

Solution 1

Port scanners usually scan in parallel so you can do the following (.net 4):

C#

List<Task> tasks = new List<Task>();

for(int i =1;i<65535;i++)
{
    Task t = Task.Factory.StartNew( () => portscan(i));
    tasks.Add(t);
}

Task.WaitAll(tasks.ToArray());

Posted 10-Aug-12 20:33pm

Mehdi Gholam

Updated 10-Aug-12 20:34pm

v2

Comments

Gajendra Yadav 12-Aug-12 10:41am

This solution is nice but i want in .net 3.5.

Mehdi Gholam 12-Aug-12 11:18am

You can use a ThreadPool : http://msdn.microsoft.com/en-us/library/3dasc8as%28v=vs.80%29.aspx