Wsrtjtyk

I am trying to write a routine in powershell which will listen on a UDP port, then exit when a key is pressed. The problem I have is that the program will only exit after a datagram has been read.

I.e. It will read n values, user will hit F12, program will wait until it gets the n+1th value, then exit.

What should happen is: reads n values, user will hit F12, program should shut down.

$endpoint = New-Object System.Net.IPEndPoint ([IPAddress]::Any, $port)

$continue = $true

while($continue)

{



    if ([console]::KeyAvailable)

    {

        echo "Exit with F12";

        $x = [System.Console]::ReadKey() 



        switch ( $x.key)

        {

            F12 { $continue = $false }

        }

    } 

    else

    {



        $socket = New-Object System.Net.Sockets.UdpClient $port

        $content = $socket.Receive([ref]$endpoint)

        $socket.Close()

    [Text.Encoding]::ASCII.GetString($content)

    }    

}

I'm completely new to Powershell, so maybe this isn't possible. The rest of the code has been stolen from other answers here.

A solution that uses the ReceiveTimeout property, which is mentioned in the @bluuf's comment:

$p = 17042

$e = New-Object System.Net.IPEndPoint ([System.Net.IPAddress]::Any, $p)

$u = New-Object System.Net.Sockets.UdpClient $p

$u.Client.ReceiveTimeout = 100

try

{

  for()

  {

    try

    {

      $b = $u.Receive([ref]$e)

      $s = [System.Text.Encoding]::ASCII.GetString($b)

      Write-Host $s

    }

    catch [System.Net.Sockets.SocketException]

    {

      if ( $_.Exception.SocketErrorCode -ne 'TimedOut' )

      {

        throw

      }

    }

    if ( [System.Console]::KeyAvailable )

    {

      $x = [System.Console]::ReadKey($true)

      if ( $x.key -eq [System.ConsoleKey]::F12 )

      {

        Write-Host 'Exit with F12'

        break

      }

    }

  }

}

finally

{

  $u.Close()

}

The asynchronous version might look like this:

if( -not('CallbackEventBridge' -as [type]) )

{

  Add-Type @'

    using System;



    public sealed class CallbackEventBridge

    {

      public event AsyncCallback CallbackComplete = delegate { };



      private CallbackEventBridge() {}



      private void CallbackInternal(IAsyncResult result)

      {

        CallbackComplete(result);

      }



      public AsyncCallback Callback

      {

        get { return new AsyncCallback(CallbackInternal); }

      }



      public static CallbackEventBridge Create()

      {

        return new CallbackEventBridge();

      }

    }

'@

}

$sb = {

  param($ar)

  $e = $ar.AsyncState.e

  $u = $ar.AsyncState.u

  $b = $u.EndReceive($ar, [ref]$e)

  $s = [System.Text.Encoding]::ASCII.GetString($b)

  Write-Host $s

  $ar.AsyncState.completed = $true

}

$bridge = [CallbackEventBridge]::Create()

Register-ObjectEvent -InputObject $bridge -EventName CallbackComplete -Action $sb > $null

$p = 17042

$e = New-Object System.Net.IPEndPoint ([System.Net.IPAddress]::Any, $p)

$u = New-Object System.Net.Sockets.UdpClient $p

$state = @{e = $e; u = $u; completed = $true}

try

{

  for()

  {

    if( $state.completed )

    {

      $state.completed = $false

      [void]$u.BeginReceive($bridge.Callback, $state)

    }

    if ( [System.Console]::KeyAvailable )

    {

      $x = [System.Console]::ReadKey($true)

      if ( $x.key -eq [System.ConsoleKey]::F12 )

      {

        Write-Host 'Exit with F12'

        break

      }

    }

    [System.Threading.Thread]::Sleep(100)

  }

}

finally

{

  $u.Close()

}

Learn more about the CallbackEventouBridge class in the PowerShell 2.0 – Asynchronous Callbacks from .NET article by Oisin Grehan.

Both versions can be tested with the following code snippet:

$p = 17042

$u = New-Object System.Net.Sockets.UdpClient

$b = [System.Text.Encoding]::ASCII.GetBytes('Is anybody there')

$u.Connect('localhost', $p)

[void]$u.Send($b, $b.Length)

$u.Close()