RetroArch 1.4.1 - How to Host Netplay Sessions
This is a quick video showing how to download free/homebrew content from RetroArch's online updater and then initiate a netplay host instance. You can't see it in this video, but once the hosting is initiated, it is announced in the netplay lobby for others to join and, as of the 1.4.0 release, the host can continue playing while new players can jump in at any time (that is, you no longer have to stare at a black screen until the client joins).

Just launch your content like normal, go back into the quick menu, go to 'netplay' and then start hosting.

Music is phib3r optik's' "Happy day"

Licensed Creative Commons — Attribution 3.0 Unported— CC BY 3.0