# MQTT V2 The Enterprise MQTT broker enables you to subscribe to vehicle data updates and get them pushed to your application using the [MQTT protocol](https://mqtt.org/). {% hint style="info" %} **Endpoint URL** The MQTT broker URL is `mqtt-v2.high-mobility.com:8883` for live and sandbox vehicle data {% endhint %} ### Topic and message structure All messages that are published into single topics. Here's an example of the JSON that would be sent for the odometer, coordinates and altitude data: Topic: `live/level13/00000000-0000-0000-0000-000000000000` ```json { "version": 2, "application_id": "00000000-0000-0000-0000-000000000000", "message_id": "4F02FFB01650060FA8888E5C3ED46FF2A0E4A49EACF1A92E264CD0C137971B28", "vin": "EXV10000000", "data": { "diagnostics": { "odometer": [ { "data": { "unit": "kilometers", "value": 19201.01 } } ] }, "vehicle_location": { "altitude": [ { "data": { "unit": "meters", "value": 63 }, "timestamp": "2025-08-12T16:07:48.000Z" } ], "coordinates": [ { "data": { "latitude": 11.572, "longitude": 8.487 }, "timestamp": "2025-08-12T16:07:48.000Z" } ] } } } ``` #### Message Here is the JSON format that is used for every message that is published. All `data` objects, that hold the specific car data payload, are formatted according to the [Streaming Schema V2](/api-references/data/streaming-schema-v2.md) ``` { "message_id": {Unique Message ID: string}, "application_id": {application uuid} "version": 2, "vin": {Vehicle Identification Number: string}, "data": {Auto API Schema: object} } ``` {% hint style="info" %} Our system is designed to guarantee at-least-once delivery of each message. Please consider the possibility that a `message_id` is delivered more than once. {% endhint %} ### Authentication Head to your project's "API Credentials"->"Streaming" section. Select "MQTT V2(Enterprise)" and click the "Save and update" button.
After that you are able to download certificate via "Add MQTT V2 Client Certificate" section. {% hint style="warning" %} Few important notes: * When you switch the streaming method, it takes \~1h for the change to propagate, during that period you still receive the data using your previous streaming method * You can only download 5 client certificate per project per environment. If you are in a situtuon which you need more, please contact us [Help Center](https://docs.high-mobility.com/help-center/) * Currently you are not able to revoke client certificates, we are working on the implementation. {% endhint %} ### Connect {% hint style="danger" %} The client id format and shared subscription format must follow the documentation. We keep the right to enforce them via broker in future. {% endhint %} The file you downloaded in the previous step also includes a file called `snippet.txt`, which contains the required options to run an MQTT client from the terminal using `mosquitto_sub`. You may use any MQTT client software or library you prefer. When connecting. Do not omit any of the suggested options; otherwise, your mqtt client may miss some vehicle data. The following example shows how `mosquitto_sub` is used to both connect and subscribe to all messages: ```bash mosquitto_sub \ --cafile ca_crt.pem \ --cert client_crt.pem \ --key client_key.pem\ --host mqtt-v2.high-mobility.com \ --port 8883 \ --qos 1 \ -V 5 \ --id '879577a3-b25f-4a28-8c0e-7effcc7682a2-sandbox-' \ --disable-clean-session \ --topic '$share/879577a3-b25f-4a28-8c0e-7effcc7682a2/sandbox/level13/879577a3-b25f-4a28-8c0e-7effcc7682a2#' ``` The following parameters are needed for the connection: * `--cafile`, `--cert` , `--key` which you can find in the zip file. * `-qos`: Set the QoSto 1 in order to guarantee that a message is delivered at least once. * `-V` : Set the MQTT version to 5. While our broker support MQTT 3, we highly recommend to use version 5. * `--id`: Client ID. Please use your `--` as suffix. * `--disable-clean-session` : This option is needed to queue your data in the broker when your mqtt client is down. Please refer to rest the doc about the max queue size. * `--topic` : the topic include share group name `$share/879577a3-b25f-4a28-8c0e-7effcc7682a2` and the topic we want to subscribe to `sandbox/level13/879577a3-b25f-4a28-8c0e-7effcc7682a2/#`. You can read more about shared subscription at [here](https://docs.hivemq.com/hivemq/latest/user-guide/shared-subscriptions.html). {% hint style="danger" %} The client id format and shared subscription format must follow the documentation. We keep the right to enforce them via broker in future. {% endhint %} {% hint style="info" %} Each client certificate can be used for as many active connections as you need. The only limitation is that you cannot connect two clients with the same client\_id to an MQTT broker at the same time. We Suggest to use client with the following format: `-` {% endhint %} ### Subscribe Once you have connected, go ahead and subscribe to any topic path that matches your application id. Here are a few common use-cases: * To subscribe to all data updates, pass in `live/level13/{application_id}`. Replace `live` with `sandbox` if you are working with the simulator. * Use [MQTT shared subscriptions](https://docs.hivemq.com/hivemq/latest/user-guide/shared-subscriptions.html) to distribute messages across multiple consumers and speed up data ingestion. * With a shared subscription, messages are **load-balanced** between consumers in the same group, increasing overall throughput. * The shared subscription group has a **queue size of 500,000 messages** (as opposed to **10,000 messages** for a non-shared subscription). {% hint style="info" %} **HEADS UP** * Please note that the the data is not guaranteed to be delivered in a chronological order. The timestamp of each MQTT message payload will always tell you at what time the data was generated in the vehicle. * If your consumers aren’t fast enough to keep up, older messages will be dropped once the queue limit is reached. {% endhint %} You will now get vehicle data delivered to you for all vehicles that have approved access grants. To receive an access grant, have a look at the [Fleet Clearance](/docs/getting-started/fleet-clearance.md) guide depending on your specific application. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.high-mobility.com/docs/vehicle-data/mqtt-v2.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.