Test All DC Ports Async

$list = New-Object System.Collections.Generic.List[object](4)
$maxRunspaces = 20
$servers = Get-ADDomainController -Filter *
$testPorts = @(389, 636, 3268, 3269)

# Set up the runspace pool and powershell script
$rsPool = [runspacefactory]::CreateRunspacePool(1, $maxRunspaces)
$rsPool.ApartmentState = "STA"
$rsPool.ThreadOptions = "ReuseThread"
$rsPool.Open()
$code = {
    param ($Server, $Port)

    Test-NetConnection -ComputerName $Server -Port $Port
}

# Add a runspace'd powershell instance for every server on each specified port
foreach ($s in $servers) {

    foreach ($port in $testPorts) {

        $psInst = [powershell]::Create().AddScript($code).AddParameter("Server", $s.HostName).AddParameter("Port", $port)

        $psInst.RunspacePool = $rsPool

        $list.Add([pscustomobject]@{
            PowerShell = $psInst
            Runspace = $psInst.BeginInvoke()
        })
    }
}

$allResults = New-Object System.Collections.Generic.List[psobject]($servers.Count * 4)

# As long as there is one job still left in the list, keep looping and checking for completed jobs.
# Add the results from each job into a final list.
while ($list.Count -gt 0) {

    for ($i = $list.Count - 1; $i -ge 0; $i--) {

        $job = $list[$i]
        if ($job.Runspace.IsCompleted) {

            $results = $job.PowerShell.EndInvoke($job.Runspace)
            $job.PowerShell.Dispose()
            [void] $list.Remove($job)
            if ($results.Count -gt 0) {

                $allResults.AddRange($results)
            }
        }
    }
    Start-Sleep -Milliseconds 200
}
$allResults