Binary LWT message

[fpagliughi]

Why does the C library only allow for a text LWT message payload, through a const char* message instead of a const void* payload and corresponding payload length? Does the MQTT standard prevent you from using a binary LWT payload?

[guilhermeferreira]

According to the MQTT v3.1 protocol specification [http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html] the Will Message "is UTF-8 encoded [character string] in the CONNECT message [...] The message must therefore only consist of 7-bit ASCII characters."

But, to me, the MQTT v3.1.1 Protocol [http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html], section 3.1.3.3, is not very clear : "The Will Message defines the Application Message that is to be published to the Will Topic [...] This field consists of a two byte length followed by the payload for the Will Message expressed as a sequence of zero or more bytes. The length gives the number of bytes in the data that follows and does not include the 2 bytes taken up by the length itself."

If the v3.1.1 description says the same thing as the v3.1, then its correct to define it as const char*. However, if the v3.1.1 allows arbitrary bytes, then I guess it should be const unsigned char*, right?

Anyone with a deeper understand of the protocol could clarify this?

[guilhermeferreira]

There is another issue open for the same problem, #34.

[icraggs]

I'll add the ability to send binary LWT payloads, as well as passwords (PR #159). "Zero or more bytes" means that any data should be able to be sent.

[icraggs]

Update added to the develop branch, for release in June.

[icraggs]

I think this issue is fixed - closing.