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Making a custom MQTT client
As I’m finally getting my realtime transit app ready for public release, it’s a good time to go through some things I’ve learned while open sourcing my code for the first time. Transporter uses MQTT to receive vehicle data updates from the Digitransit APIs. While it’s possible to just repeatedly pull this data, there are just too many vehicles shown on the map simultaneously. The MQTT feed itself publishes JSON which contains vehicle coordinates, delay compared to schedule, heading, next stop and other useful information.