Get-AvailableIPv4Addresses.ps1

Function Get-AvailableIPv4Address {
    param (
        [System.Collections.ArrayList] $IPRange
    )

    $MaxThreads = 30
    $ScriptBlock = {
        Param (
        [String]$IPAddress
        )
        Test-Connection -ComputerName $IPAddress -Count 1 -Quiet
    }
 
    $RunspacePool = [RunspaceFactory]::CreateRunspacePool(1,$MaxThreads)
    $RunspacePool.Open()
    $Jobs = @()

    $IPRange | % {
       $Job = [powershell]::Create().AddScript($ScriptBlock).AddArgument($_)
       $Job.RunspacePool = $RunspacePool
       $Jobs += New-Object PSObject -Property @{
          IPAddress = $_
          Pipe = $Job
          Result = $Job.BeginInvoke()
       }
    }
 
    While ( $Jobs.Result.IsCompleted -contains $false) {
        Start-Sleep -Seconds 1
    }
 
    $Results = @()
    ForEach ($Job in $Jobs)
    {
        if (-not $Job.Pipe.EndInvoke($Job.Result)) {
            $job.IPAddress
        }
    }

}

$IPRange = New-Object System.Collections.ArrayList
1 .. 254 | % { $IPRange.Add("192.168.10.$_") | Out-Null }
$IPRange = @(Get-AvailableIPv4Address -IPRange $IPRange)