I prefer the I-Portals to any other portal I've used in Trainz. And, they are not just for sending trains to another user via the internet. That was one of the original purposes for them, but there were lots of problems related to that and it never seemed to become very popular. On any route I download or create I install I-Portals anywhere a track terminated at the edge or end of a route. My routes are set to receive and send trains from/to other routes via the I-Portals. All my routes are within the same PC and I have never sent anything to another route via the internet. I-Portals are easy to set up and very reliable, at least through TS-2010. I cannot speak for TS-12. With a few exceptions, a train exiting one route and arriving on another route will retain the same car numbers and loads. You can also use these to turn a train or have it appear somewhere else in the same route. If you configured a train to exit Route 1 and arrive at a specific portal on Route 2, but change your mind and now want to direct it to another portal (or the same portal) then you can easily do that while the session is running (i.e., this does not require a change in the session setup in surveyor).
I've had problems with some of the newer portals designed to "eat" trains and "spit out" new trains on some interval. The new trans were often incomplete and without loads and I sometimes got "ghost trains" I could not get control over unless I rammed them with a locomotive that I did have control over. These "ghost trains" (usually just a couple of engines) would plod down the mainline at less than 5 MPH and would become apparent when all your AI trains started getting backed up and stopping.
If you've never tried them, place one on a route in Surveyor and use the ? mark icon and click on the I-Portal. Here you can give the portal a unique name. The I-Portal ID needs to be unique also since it is used at other I-Portals as the Destination ID. Send to User *NOBODY* applied only to sending a train to someone else via the internet. Destination I-Portal ID is the I-Portal ID to which you are sending the train. Send Trains Via the Internet or Only Within this Computer are your next options. I always use Only Within this Computer. I'm not exactly sure what Check for Trains does except possibly check for a new train arriving in the portal at the user specified number of minutes and provide you with an alert. I don't use it. The last setting for Driver Mode After Create (Manual or Auto) is self explanatory. I have always used manual where the train recreates itself and drives just clear of the portal and stops to await new orders. Trains are not created until you direct them to be. A portal queue can hold several trains in it awaiting your directions to "spit them out".
