code: @Nonnull
    public final JettyStarter setStopPort (@Nonnegative final int nStopPort)
    {
      ValueEnforcer.isGT0 (nStopPort, "StopPort");
      m_nStopPort = nStopPort;
      return this;
    }
docs: Set the port on which the "stop monitor" should be running. Defaults to
  {@link #DEFAULT_STOP_PORT}. When running multiple Jettys at once, each
  instance must use it's own stop port. If this is set here, it must also be
  set in {@link JettyStopper}.
  
  @param nStopPort
  The stop port to be used. Must be &gt; 0.
  @return this for chaining