Media Server using rtpm input from another server?

Hi guys i'm interested in streaming content from a rtpm source to a stb (like a mag 254) for an iptv stream and i don't know where to start, i've looked online but i didn't find anything useful. the most useful thing is a 3-line string that i don't know where to put. I've also whatched a video on lynda.com for a HDS VOD stream but i don't need that. i think that i need a Adobe media server 101 curse. can you explain me that? Or give me useful links. Another problem that i wouldn't have is that if the rtmp link changes how does fms to grab it automatically?

Thanks.