If you make a reservation for a place to stay at Porto, something I always advise for larger towns and cities, send them an email to ask permission to post something to them to await your arrival.
Use an online translator, like Google or the Microsoft version, to compose a readable message in Portuguese (not Spanish... Doh!). I have often used this approach in both Portugal and Spain. So far, no hotel has refused me.
Typically, I send medicines and other consumables ahead so I can refill every two weeks. I usually send luggage with post-Camino consumables, clothes, etc. direct to Santiago. In this regard, I will either ship the stuff to Ivar, or to a hotel I have already reserved.
This will not work for albergues, generally.
Other than this, the only possible option I can think of is the "Postal Restante" system, or whatever it is correctly called in Portugal. Using this capability, you mail a parcel, etc. to yourself c/o the post office address. They hold the parcel for you, according to their policies.
If anyone on the forum knows how the Portuguese system functions in this regard, or if they do it at all (Post Restante), please contribute. I would also like to know. I do not recall the Portugues system being discussed before.
For me, sending something ahead to a reserved hotel works best. But each person is different.
Hope this helps.