# File lib/net/ssh/gateway.rb, line 85
  def shutdown!
    return unless active?

    @session_mutex.synchronize do
      # cancel all active forward channels
      @session.forward.active_locals.each do |lport, host, port|
        @session.forward.cancel_local(lport)
      end
    end

    @active = false
    
    @thread.join
    @session.close
  end