Hello Hannes, We used broker as it is a widely accepted term in the MQTT Community for "server" e.g., majority of the provider would list also a broker implementation to refer to their server implementation.
With respect to whether 3.1,1 clients talking to v5, there may be some issues. This is what the spec says: *Non-normative Comment* If the Server distributes Application Messages to Clients at different protocol levels (such as MQTT V3.1.1) which do not support properties or other features provided by this specification, some information in the Application Message can be lost, and applications which depend on this information might not work correctly. The spec also defines a protocol version error message: If the [Client's] Protocol Version [in the CONNECT packet] is not 5 and the Server does not want to accept the CONNECT packet, the Server MAY send a CONNACK packet with Reason Code 0x84 (Unsupported Protocol Version) and then MUST close the Network Connection So, whether a broker provides dual support would depend on the provider. E.g., the Mosquitto broker supports the different protocol versions. Thanks, --Cigdem On Tue, Feb 25, 2020 at 10:01 AM Hannes Tschofenig < [email protected]> wrote: > Hi Cigdem, Hi Anthony, Hi Paul, > > Why are you using the term MQTT broker? My understanding of the MQTT spec > is that there are only clients and servers - nothing more. > > Is a MQTT v3.1.1 client able to talk to a MQTT v5 server? Would a MQTT > v3.1.1 client talk to a MQTT v5 client via a server that supports both > v3.1.1 and v5? > > Ciao > Hannes > > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. > > _______________________________________________ > Ace mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/ace >
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