The DMAP protocol is a specialized HTTP protocol, which performs two functions. It sends a list of items and it streams requested items to clients. There are also provisions to notify the client of changes to the server. Requests are sent to the server by the client in form of URLs and are responded to with data in application/x-dmap-tagged mime-type. Services such as iTunes and iPhoto uses the ZeroConf (also known as Bonjour) service to announce itself and discover DMAP services on a local subnet.
A range of open- and closed-sourced applications have successfully reversed engineered parts of the protocol