System.Net.Sockets.TcpClient slow in powershell

Question

try
{
  $tcp = new-object System.Net.Sockets.TcpClient

  $tcp.ReceiveTimeout = 500
  $tcp.SendTimeout = 500

  $tcp.Connect('127.0.0.1',80)
  Write-Host "Connection possible!"
  $tcp.close()
}
catch
{
    Write-Host "Cannot connect!"
    $_.Exception.Message
}

Measure-Command - 21 seconds (always 21!)

If $tcp.Connect('127.0.0.1',80,$Null)

Measure-Command - 10 milliseconds

Why?

I know that there should be no $Null param but why is it fast with it ?

$tcp.Connect take two parameters not three https://msdn.microsoft.com/en-us/library/d7ew360f(v=vs.110).aspx. With three parameters raise exception:Cannot connect! Cannot find an overload for "Connect" and the argument count: "3". It take 1 second to run with success connection in my machine with 2 parameters. — M.Hassan, Oct 14 '16 at 16:40

score 3 · Accepted Answer · edited May 23 '17 at 10:29

I know that there should be no $Null param but why is it fast with it ?

Because your code is broken.

try 
{

}
catch
{
}

is catching every possible error, and hiding the error messages.

Your first code, the error is a genuine TCP connection which timed out after a ~30 second wait, and the connection really has failed.

Your second code, the error is "Cannot find an overload for Connect which takes 3 parameters" - but you hide the error and wrongly print 'cannot connect' instead. This is misleading you. It's not faster, it's broken.

The send and receive timeouts are not for connections, they are timeouts for the methods to sending and receive data. There is no way to change the connection timeout with the .connect() method, you need to make an asynchronous connection without your own timeout to do that.

e.g. How to set the timeout for a TcpClient? and How to configure socket connect timeout (both C#, but still .Net and the ideas are applicable to PowerShell).

And this https://superuser.com/questions/805621/test-network-ports-faster-with-powershell which has an answer for PowerShell

Thanks, if (!$tcp.ConnectAsync("234234", 80).Wait(500)) {'fail'} solves everything — Igor Kuznetsov, Oct 14 '16 at 17:53

Endorphinex · Answer 2 · 2016-10-14T16:12:31.553

0

$tcp.Connect('127.0.0.1',80,$Null) throws an exception Cannot find an overload for "Connect" and the argument count: "3". Read more here: MDSN Documentation

edited Oct 14 '16 at 16:12

answered Oct 14 '16 at 16:08

Endorphinex

23
2
11

I see it. But why it work fast with $null ? I mean it work fast both ways if port is really OK. If not - only $Null variant works fast – Igor Kuznetsov Oct 14 '16 at 16:11
I don't know. On my computer this code ended after milliseconds – Endorphinex Oct 14 '16 at 16:14
1

@IgorKuznetsov Does it succeed or error? I think the point Endorphinex is making is that the code ends fast because it errors out, not that it returns valid results. – JClaspill Oct 14 '16 at 16:14
This may take more or less, depending on network card and internet connection speed. – Endorphinex Oct 14 '16 at 16:15
@JClaspill This bigger code work as intended, but this smaller one throws me an exception – Endorphinex Oct 14 '16 at 16:17
It is the same on my windows server at work.. Without $Null code took 21 seconds... Cant see any logic – Igor Kuznetsov Oct 14 '16 at 16:18
1

Maybe, with `$Null` PS sees it, and immediately throws an exception, but without `$Null` it must wait until it connect to this address... – Endorphinex Oct 14 '16 at 16:22
1

Found solution. There should be no quotes near IP address. '127.0.0.1' works 21 seconds.... $tcp.Connect(127.0.0.1,80) works for 7 milliseconds :)) – Igor Kuznetsov Oct 14 '16 at 17:16
Hmm, no, quotes need.. Exception calling "Connect" with "2" argument(s): "Value cannot be null... – Igor Kuznetsov Oct 14 '16 at 17:20

System.Net.Sockets.TcpClient slow in powershell

2 Answers2