1...999 | ForEach-Object {
    $port = $_
    $tcpClient = New-Object System.Net.Sockets.TcpClient
    $connectTask = $tcpClient.BeginConnect("123.456.789.012", $port, $null, $null)
    $waitHandle = $connectTask.AsyncWaitHandle
    $result = $waitHandle.WaitOne(300) # 300 milliseconds = 0.3 seconds
    $waitHandle.Close()

    if ($result -eq $true) {
        $tcpClient.EndConnect($connectTask)
        Write-Output "Port $port is open."
    }
    else
    {
        Write-Output "Port $port is closed."
    }

    $tcpClient.Close()
}