Semtech UDP packet-forwarder

The Semtech UDP packet-forwarder backend abstracts the UDP protocol.

It is compatible with:

  • v1 of the protocol
  • v2 of the protocol
  • Modified format used by the Kerlink iBTS containing the (encrypted) fine-timestamp


When the semtech_udp backend has been enabled, make sure your packet-forwarder global_conf.json or local_conf.json is configured correctly, under gateway_conf, the server_address, serv_port_up and serv_port_down must be configured so that data is forwarded to the ChirpStack Gateway Bridge instance.

"gateway_conf": {
	"gateway_ID": "AA555A0000000000",
	"server_address": "localhost",
	"serv_port_up": 1700,
	"serv_port_down": 1700,


The ChirpStack Gateway Bridge can be deployed either on the gateway (recommended) and "in the cloud". In the latter case, multiple gateways can connect to the same ChirpStack Gateway Bridge instance.

When the ChirpStack Gateway Bridge is deployed on the gateway, you will benefit from the MQTT authentication / authorization layer and optional TLS.

Prometheus metrics

The Semtech UDP packet-forwarder backend exposes several Prometheus metrics for monitoring.


The number of UDP packets sent by the backend (per packet_type).


The number of UDP packets received by the backend (per packet_type).


The number of gateway connections received by the backend.


The number of gateways that disconnected from the backend.