Meshtastic networks in different locations beyond the reach of LoRa can be easily bridged together using MQTT. The simplest option is to connect your mesh to the official Meshtastic MQTT broker. This makes your devices appear on the world map, and provides a copy of your mesh traffic, translated into JSON. All you have to do to join the public MQTT server is to Enable MQTT and set Uplink and Downlink on the channels that you want to share over MQTT. The default device configuration using the public MQTT Server is encrypted.
When MQTT is turned on, you are potentially broadcasting your entire mesh's traffic onto the public internet. This includes messages and position information.
The default channel (LongFast) on the public MQTT server usually has a lot of traffic. Your device may get overloaded and may no longer function properly anymore. It is recommended to use a different channel or to use your own MQTT server if you experience issues.
When MQTT is enabled, the Meshtastic device simply uplinks and/or downlinks every raw protobuf MeshPacket that it sees to the MQTT broker, encapsulated in a [ServiceEnvelope protobuf](https://buf.build/meshtastic/protobufs/docs/main:meshtastic#meshtastic.ServiceEnvelope). In addition, some packet types are serialized or deserialized from/to JSON messages for easier use in consumers. All packets are sent to the broker, whether they originate from another device on the mesh, or the gateway node itself.
The payload is a raw protobuf, whose definitions for Meshtastic can be found [here](https://github.com/meshtastic/protobufs/blob/master/meshtastic). Reference guides for working with protobufs in several popular programming languages can be found [here](https://protobuf.dev/reference/). Looking at the MQTT traffic with a program like `mosquitto_sub` will tell you it's working, but you won't get much useful information out of it. For example:
If [encryption_enabled](/docs/configuration/module/mqtt#encryption-enabled) is set to true, the payload of the MeshPacket will remain encrypted with the key for the specified channel.
If [JSON is enabled](/docs/configuration/module/mqtt/#json-enabled), packets from the following [port numbers](/docs/development/firmware/portnum) are serialized to JSON: `TEXT_MESSAGE_APP`, `TELEMETRY_APP`, `NODEINFO_APP`, `POSITION_APP`, `WAYPOINT_APP`, `NEIGHBORINFO_APP`, `TRACEROUTE_APP`, `DETECTION_SENSOR_APP`, `PAXCOUNTER_APP` and `REMOTE_HARDWARE_APP`. These are then forwarded to the topic:
- "`id`" inside the payload of a `NODEINFO_APP` message is the user ID of the node that sent it, which is currently just the hexadecimal representation of the node number.
- "`hardware`" is the [hardware model](https://github.com/meshtastic/protobufs/blob/master/meshtastic/mesh.proto#L215) of the node sending the `NODEINFO_APP` message.
- "`longname`" is the long name of the device that sent the `NODEINFO_APP` message.
- "`shortname`" is the short name of the device that sent the `NODEINFO_APP` message.
- "`sender`" is the user ID of the gateway device, which is in this case the same node that sent the `NODEINFO_APP` message (the hexadecimal value `7efeee00` represented by an integer in decimal is `2130636288`).
- "`timestamp`" is the Unix Epoch when the message was received, represented as an integer in decimal.
- "`to`" is the node number of the destination of the message. In this case, "-1" means it was a broadcast message (this is the decimal integer representation of `0xFFFFFFFF`).
- "`type`" is the type of the message, in this case it was a `NODEINFO_APP` message.
The `from` field can thus be used as a stable identifier for a specific node. Note that in firmware prior to 2.2.0, this is a signed value in JSON, while in firmware 2.2.0 and higher, the JSON values are unsigned.
If the message received contains valid JSON in the payload, the JSON is deserialized and added as a JSON object rather than a string containing the serialized JSON.
**Sent messages** will be checked if the MQTT payload contains a valid JSON-encoded envelope:
```json
{
"sender": "SENDER",
"payload": {
"key":"value"
...
}
}
```
`sender` and `payload` fields are required for a valid envelope. If a valid MQTT message is found, the message is sent over the radio as a message of type `TEXT_MESSAGE_APP` with the serialized `payload` value in the message payload.
- Connect your gateway node to wifi, by setting the `network.wifi_ssid`, `network.wifi_psk` and `network.wifi_enabled` preferences.
- Alternatively use the RAK4631 with Ethernet Module RAK13800, by setting `network.eth_mode` and `network.eth_enabled`.
- Configure your broker settings: `mqtt.address`, `mqtt.username`, and `mqtt.password`. If all are left blank, the device will connect to the Meshtastic broker.
- Set `uplink_enabled` and `downlink_enabled` as appropriate for each channel. Most users will just have a single channel (at channel index 0). `meshtastic --ch-index 0 --ch-set uplink_enabled true`
Any meshtastic node that has a direct connection to the internet (either via a helper app or installed WiFi/4G/satellite hardware) can function as a "Gateway node".
Gateway nodes (via code running in the phone) will contain two tables to whitelist particular traffic to either be delivered toward the internet, or down toward the mesh. Users that are developing custom apps will be able to customize these filters/subscriptions.
Since multiple gateway nodes might be connected to a single mesh, it is possible that duplicate messages will be published on any particular topic. Therefore, subscribers to these topics should
