Back in the Windows Mobile / Symbian days, in 2007, I've already published a full roundup of then-current UPnP (desktop) server and mobile client apps (see THIS / THIS). Now, let's take a look at how it is done on the iDevice (iPad [Mini] / iPhone / iPod touch)!
As you may have guessed, the stock video player shipped with iOS, “Videos”, doesn't support accessing UPnP (also known as DLNA; in this article, I refer to it as “UPnP”) servers. That is, you'll need to use third-party apps on your iDevice. Fortunately, there are several of them.
1. What can you use UPnP for on iOS?