code: func (net *Network) DidSend(sender, receiver enode.ID, proto string, code uint64) error {
  	msg := &Msg{
  		One:      sender,
  		Other:    receiver,
  		Protocol: proto,
  		Code:     code,
  		Received: false,
  	}
  	net.events.Send(NewEvent(msg))
  	return nil
  }
docs: // DidSend tracks the fact that "sender" sent a message to "receiver"