====== MQTT Server ======

All receivers report their data to a central MQTT broker, which feeds the live map at [[https://opentrafficmap.org|opentrafficmap.org]].

===== Connecting =====

  * The current connection string (host and port) is defined in the firmware: [[https://codeberg.org/opentrafficmap/its-g5-receiver-firmware/src/branch/main/main/config.c|its-g5-receiver-firmware/main/config.c]]
  * **Publishing requires no username or password.**
  * Every node identifies itself by its **node name** — by default the Ethernet MAC address of the ESP32 (e.g. ''aabbccddeeff''). We are happy to replace it with a friendly name in our database; see [[en:node_registration|Node Registration]].

===== Topics =====

Each node publishes under ''its/nodeXXX/...'', where ''nodeXXX'' is the **node ID** — currently simply an ascending number. You can find your node's ID in the self-service portal (see [[en:node_registration|Node Registration]]):

^ Topic ^ Content ^
| ''its/nodeXXX/packet/json'' | received C-ITS packets as JSON |
| ''its/nodeXXX/stats'' | node statistics / telemetry |

To subscribe to **all** messages of a node, the wildcard ''its/nodeXXX/#'' should work as well by now.

===== Subscribing to your node =====

The self-service portal shows credentials that allow you to subscribe to the messages of your own node — see [[en:node_registration|Node Registration]]. You can use any MQTT client; a list of clients for Linux, Windows, and macOS is in the [[en:faq|FAQ]].

===== What is published =====

  * the received raw C-ITS frames (CAM, DENM, MAPEM, SPATEM, IVIM — see [[en:c-its:start|C-ITS]])
  * node telemetry and status information

If you built your own receiver, there are several ways to get your data onto the broker — see [[en:software:transmission_methods|Transmission Methods]].