Automatically pulling data from a PowerShell job while running

jobs, powershell, udp

Solution

You can return data from a job by raising an event and forwarding it back to the local session.

Here is an example:

 $job = Start-Job -Name "ReturnMessage" -ScriptBlock {
     # forward events named "MyNewMessage" back to job owner
     # this even works across machines
     Register-EngineEvent -SourceIdentifier MyNewMessage -Forward

     while($true) {
         sleep 2
         $i++
         $message = "This is message $i."
         # raise a new progress event, assigning to $null to prevent
         # it ending up in the job's output stream
         $null = New-Event -SourceIdentifier MyNewMessage -MessageData $message
     }
 }

$event = Register-EngineEvent -SourceIdentifier MyNewMessage -Action {
    Write-Host $event.MessageData -ForegroundColor Green
}

<# Run this to stop job and event listner
$job,$event| Stop-Job -PassThru| Remove-Job
#>

Note that you can still type at the prompt while the job is running. Execute the code in the block comments to stop the job and event listner.

Problem

While trying to do something quite possibly beyond the means of PowerShell I seem to have ran into a brick wall. I have a main form script, which orchestrates most of my functions but I need another script to open a listener (system.Net.Sockets.Udpclient.Receive) and keep feeding in information to a textbox in the main form throughout the entire program's running. For the life of me I can't get around this daft non-child environment that jobs suffer from; no dot sourcing, no global scoped variables, nothing. I can put an object-listener on it for statechanged to completion and then open another listener and try and bodge this way but it will get very messy and unreliable. As a workaround I would love a TCP/UDP listener which doesn't hang the application for a response, an event to pull on hasmoredata or a way of updatign the textbox in the main script from within the job.

Original source