The DLNA acronym is short for Digital Living Network Alliance, a standard to which more than 250 technology companies and are subscribed whose mission is to share online content from any device, regardless of brand or model. Compatible equipment can be of any kind, including routers, TVs, hard drives, mobile phones, computers, etc., but need to be connected to a local network by WiFi or Ethernet.
In general there are three basic types of equipment with different roles within a DLNA network: a server to host multimedia files (network hard disk, a computer or mobile itself etc.), a player that will play the content (in our case the phone) and a renderer (a screen or stereo). Being all within the same network, detection should be automatic (or almost) and you just have to dissect the terminal device why we play the video file or sound.