Exiting a UDP listen routine - powershell

Question

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.

Answer 1

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()