MQTT 5.0: Authentication with only password does not work with mosquitto_pub.

[eerimoq]

Hello!

The MQTT version 5.0 specification allows a client to send a password
with no user name in the connect packet. The mosquitto_pub, and
probably mosquitto_sub, programs does now support this it seems.

Copied from the specification:

"This version of the protocol allows the sending of a Password with no
User Name, where MQTT v3.1.1 did not. This reflects the common use of
Password for credentials other than a password."

A warning is printed if a password is given but no user name. The password is not sent to the broker.

$ mosquitto_pub -V mqttv5 -t myt -m mym -d -P mypass
Warning: Not using password since username not set.
Client (null) sending CONNECT
Client (null) received CONNACK (0)
Client (null) sending PUBLISH (d0, q0, r0, m1, 'myt', ... (3 bytes))
Client (null) sending DISCONNECT

The command works when both user name and password are given.

$ mosquitto_pub -V mqttv5 -t myt -m mym -d -u myuser -P mypass
Client (null) sending CONNECT
Client (null) received CONNACK (134)
Bad User Name or Password

[ralight]

Thanks very much, I've just pushed a change that fixes this and will be part of 1.6.3.