Control packet types mqtt reserved

[Jonathas Alberto]

In the documentation, section 2.2.1 describes the types of packages and yours values, I would like to know why the values 0 and 15 are reserved?

Thanks

[Nick O'Leary]

There are 16 available values in the 4 bits of the fixed header, but the protocol only defines 14 packet types. The unused values, 0 and 15 are reserved for future versions of the protocol and shouldn't be used by proprietary implementations. Not much else to it.

Nick

On 3 September 2017 at 14:05, Jonathas Alberto <jonathas...@gmail.com> wrote:

In the documentation, section 2.2.1 describes the types of packages and yours values, I would like to know why the values 0 and 15 are reserved?

Thanks

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[Andy Stanford-Clark]

just one small comment to add to that: a long time ago we agreed that message type 0 will never be used, as that is what you’d accidentally send if you forgot to fill in the message type and just sent the default value most languages would initialise a variable to.

To avoid any unintended consequences, we agreed to mark 0 as an invalid message type.

Andy

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