OGN redistributes the aircraft position data (FLARM, OGN tracker,…) using APRS. This is a system used by Amateur Radio gurus for packet data and provides a simple and fairly clean method of subscribing to the information.
Subscribe to the APRS servers
There are several clients written in different languages to connect to the APRS servers directely.
See tags:development to find a description for your preferred language.
The APRS servers are available via TCP at aprs.glidernet.org , port 14580 for server-side filters.
The servers expect a handshake and configuration of a filter. A detailed guide on how to connect to an aprs server can be found in the APRS-IS documentation.
You need to send a keep-alive back to the server on a regular basis or your connection will be dropped. Do this by sending a line beginning with a hash and some information about your receiver.
OGN extends the APRS protocol by using APRS comment fields. This extension is called OGN-flavoured APRS.
Subscribe to gateway servers
Instead of subscribing to an aprs server directly, it is possible to get aggregated data from several sources via various APIs.