启用了TLS的mosquitto_sub

Question

I am new to MQTT and I have a frustrating problem.

I have been using MQTT.fx to subscribe to a topic; I have set the:

• Broker Address
• Port
• Client ID
• Enable SSL/TLS
• Topic

This works well, however I would like to use mosquitto_sub. I am attempting to subscribe to the same topic in the following way:

mosquitto_sub -h  host -p 8883 -t topic -i client id

This is not working for me. I am using it on a Ubuntu VM.
My powers of observation tell me that I should enable TLS, however I'm not quite sure how to do that, I have stuffed around with certificates and enabling TLS in may ways but have not got the right combo. I know it is required as if I uncheck the SSL/TLS box in MQTT.fx I am unable to connect.

I would really like to replicate what I have in MQTT.fx with mosquitto.

Answer 1

In the mosquitto_sub command, use the --capath argument to point to /etc/ssl/certs. It needs a pointer to the trusted certificates.

Answer 2

To enable SSL with mosquitto_sub you need to specify a CA certificate.

This can be done in 1 of 2 ways.

1. --cafile /path/to/a/file where the file contains the required trusted CA certificate (either on it's own or part of a concatenated set)
2. --capath /path/to/directory where the directory contains a collection of files ending in .crt which contain the CA certificates to be trusted. The ca certs should also be indexed with the c_rehash function.

Both these options are mentioned in the mosquito_sub man page as ways to enabled SSL

eg

mosquitto_sub -h host -p 8883 --cafile ca.crt -t topic -i client id