I need to buy a ticket for an international train and, apparently, there are no websites selling it.
I once remember a friend telling me that the trains uses a system, sort of, similar to the airplanes. There is a general backend computer system that allows to find schedules everywhere and also sell tickets (eg.: you can buy a ticket at any touristic agency). He also mentioned it would be possible (at least technicaly) for a train company to sell someone elses tickets on another country.
So, to wrap this, is it possible to buy a train ticket for an international train (that goes from A to B) in a third country (C)?
Edit: I tried to make the question generic, but, answering the comments, the countries A and B are Poland and Czech Republic. The country I would like to buy the ticket in (i.e. C) would be either Belgium, Netherlands, Spain or Portugal.
Note that my question is not if I can buy them online. I already asked that. My question is if I can buy them through either a travel agent or a train company (International) ticket shop.