Possible solutions to clients auto-discovering a broker:

• Zeroconf / Multicast-DNS / DNS-SD

  • a non-intrusive example using Avahi

• Anycast / a well-known IPv6 address

• DHCP option

The following sequence might be reasonable:

• Use user supplied values for server name or ip number

• Use a server name or ip number received as DHCP option (how can we apply for an official DHCP option assignment for MQTT? A: Application instructions at the end of RFC 2132. List of all current DHCP Options. Recommend Option 7 (Logging Server).

• Zeroconf to find the mqtt server

• Try mqtt.<localdomain> as server name

• Try using the ip address of the DHCP server

• Use a vendor supplied server name

Some steps may be skipped if not supported by the particular client.

Discussion of using JmDNS and MQTT

autodiscovery for mosquitto (bug tracker)