checkConnection.ps1

Start-Job -ScriptBlock {
     $ipaddress = '127.0.0.1'
     $port = 3000
     $try = 0
     $sleepTime = 10

     while(1) {
         Start-Sleep -s $sleepTime
         try {
               $connection = New-Object System.Net.Sockets.TcpClient($ipaddress, $port)
               Write-Output  "$(Get-Date -Format u) - app is running"
               $sleepTime = 5
         }
         catch {
               if ($try -eq 3) {
                   Write-Output "$(Get-Date -Format u) - app down quit"
                   exit
              } else {
                    $try = $try + 1
                    Write-Output "$(Get-Date -Format u) - app down try $try"
              }
         }
     }
}