Scan a given range of ports for a specific server. NB: Optimum group size is ~250

PortScanner.ps1

cls
workflow Test-PortOpenQuickly {
    [cmdletbinding()]
    param(
        [Parameter(Mandatory = $true)]
        [string]$ComputerName
        ,
        [Parameter(Mandatory = $true)]
        [int[]]$Ports
        ,
        [Parameter(Mandatory = $false)]
        [int$GroupSize = 250
    )
    $portGroups = InlineScript {
        [psobject]$itemCounter = [pscustomobject]@{itemNo=0;groupSize=$using:GroupSize} 
        $itemCounter | Add-Member -MemberType ScriptMethod -Name 'groupNo' -Value {
            [math]::Floor($this.itemNo++ / $this.groupSize)
        }
        write-output $using:Ports | Group-Object -Property {$itemCounter.groupNo()}
    }
    ForEach -parallel ($portGroup in $portGroups) {
        $portGroup | select -ExpandProperty group | %{
            try {
                $socket = new-object System.Net.Sockets.TcpClient -ArgumentList @('ccoportal', $_) -ErrorAction SilentlyContinue
                If($socket.Connected){
                    $Open = $true
                    $socket.Close() 
                }
            } catch {
                $Open = $false
            }
            write-output (new-object -type psobject -property @{ComputerName=$ComputerName;Port=$_;Open=$Open})
        }
    } 
}
[System.Diagnostics.Stopwatch]$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew()
Test-PortOpenQuickly -ComputerName 'myComputer' -Ports (0..65535) | ? Open | sort Port | ft ComputerName, Port, Open
$stopwatch.Stop()
$stopwatch.Elapsed

#group size 10 => ~1 hour 13 mins
#group size 100 => 30 mins
#group size 250 => 26 mins
#group size 1000 => 35 mins