OpenBridge is an open protocol to link DMR servers. Protocol designed in cooperation between BrandMeister team and Kurt OE1KBC.
OpenBridge is very simple protocol that allows to send call streams between servers.
Protocol is based on MMDVM protocol and supports DMRD packets only.

At current moment protocol doesn't solve question of routing information exchange.

Basic principals

  • No connection establishment, no keep-alives
  • DMR call streams only, multiple calls at the same time
  • Both sides should have configured end-points
  • Secured by using HMAC-SHA1 signs
  • IPv6 support

Frame format

  • DMR payload
    • 53 bytes of MMDVM's DMRD message
    • Slot bit should be clear
    • Repeater ID field should be filled with peer ID of server
    • Stream ID should identify each unique transmission
    • Sequence number should start from 0 on each transmission
    • Any kind of call is accepted (group, private, data, CSBK, etc)
  • HMAC-SHA1 signature
    • 20 bytes in length
    • Plain text key should be used
    • Key should be unique for each pair of endpoints


UDP 62035

BrandMeister Log Entries

The following log entries are samples of what typical entries look like on the BrandMeister Servers.

Start/Restart of the OpenBridge Service/Connection

Connection of OpenBridge system xxxxxxx50 ( removed
Connection address of OpenBridge system xxxxxxx50 changed (

When BrandMeister sends traffic to OpenBridge

Added route to OpenBridge system xxxxxxx50 at slot 0 (locked) by ScriptEngine / makeBridgedNetworkRouteForGroup (30-Generic.lua:89) (session xxxxxxx)

When OpenBridge sends traffic to BrandMeister

New session xxxxxxx of OpenBridge system xxxxxxxxx50 at slot 0


These are the typical issues users run into when they first setup an OpenBridge Connection. If none of the issues listed here help please open a support ticket.

Connection Issues

Q: Not seeing any traffic from BrandMeister on your OpenBridge Connection (HBLink or other server)
A: Make sure UDP Port forwarding is properly setup on your network and or verify IP address is still the same as provided to the BrandMeister Team at setup. It is recommended to choose a Static IP and or utilize a Dynamic DNS Service like NoIP if hosting on a home network or a network which issues dynamic IP addresses.