How to pass object to Get-Job subprocess as reference - powershell

Question

I need to write a powershell script that asynchronously reads from and writes to a System.IO.Ports.SerialPort object. However when writing the code to simply read from the object using Start-Job I'm getting an error. Here's my code so far:
$func = {
function CheckPort
{
param (
[parameter(Mandatory=$true,ValueFromPipeline=$true)]
[System.IO.Ports.SerialPort]$port
)
Write-Output $port.ReadLine()
}
}
$port = new-Object System.IO.Ports.SerialPort COM4, 9600, None, 8, one
$port.Open()
Start-Job -ScriptBlock {CheckPort $args[0]} -ArgumentList $port -Name “$computerName” -InitializationScript $func
When I run the code above, after I use Receive-Object to check the output of the subprocess, I see an error. It seems that instead of the $port object being passed as-is, it is first serialized then unserialized:
Error: "Cannot convert the "System.IO.Ports.SerialPort" value of type "Deserialized.System.IO.Ports.SerialPort" to type "System.IO.Ports.SerialPort"."
+ CategoryInfo : InvalidData: (:) [CheckPort], ParameterBindin...mationException
+ FullyQualifiedErrorId : ParameterArgumentTransformationError,CheckPort
+ PSComputerName : localhost
Is there anyway to pass the an argument by reference using Start-Job? $port.ReadLine() is blocking and there isn't an alternative method that can just check whether there is something to read, and I need to occasionally write to the port, so I definitely need asynchronous execution here.
I get the same error if I try $using:
$port = new-Object System.IO.Ports.SerialPort COM4, 9600, None, 8, one
$port.Open()
Start-Job -ScriptBlock {
$myPort = $using:port
Write-Output $myPort.ReadLine()
}

Answer 1

These two methods don't serialize the objects. You need PS 7 for foreach-object -parallel, but you can download start-threadjob in PS 5.
Start-ThreadJob {
$myPort = $using:port
$myPort.ReadLine()
} | receive-job -wait -auto
foreach-object -parallel {
$myPort = $using:port
$myPort.ReadLine()
}