static void Main(string[] args)
{
   // create the parser
   var parser = new CommandLineParser<ServerOptions>();
   
   // configure the options using the Fluent API
   parser.Configure(options => options.Port)
      .Name("p", "port")
      .Description("The port of the server")
      .Required();

   // parse
   var parsed = parser.Parse(args);

   // check for parsing errors
   if (parsed.HasErrors)
   {
      Console.ReadKey();

      return -1;
   }

   Console.WriteLine($"Parsed port is {parsed.Result.Port}");
}

private class ServerOptions
{
   // options
   public int Port { get; set; }
}