Cannot recieved any payload when topic set to #

EMQX
1

Hi I used nodered as mqtt client, I can connect to my EMQX broker successfully (pubs and subs).
however I noticed some strange characteristic of EMQX, when topic was set to “#” which means I want to subscribe to all its topic, it doesn’t give me any return data. but when I specifically set the topic to “data/test” I can get my data.

image

I am new to EMQX, does it not allow the “#” as topic? I already used a lot of MQTT brokers but first time to encounter this situation in EMQX.

Hope you can help me.

Thanks and regards,
Henjoe

2

I’m afraid you didn’t subscribe successfully.

EMQX prohibits anyone from subscribing to topic # by default, in etc/acl.conf.

You can modify this file to enable you to subscribe to topic #, but we generally do not recommend this, because in the actual application process, you will find that you may receive unexpected messages.

3

Hi! Thanks for your suggestion.

I actually can subscribe to any topic, I just need to literally typed-in the topic like “topic/test”.

When I tried “topic/#” I can also recieved all my data under that “topic”, what I actually really want is to get all my data that’s why I want it to be “#”. However as you mentioned it is prohibited, is it a default configuration?

4

Yes, it’s a default rule in etc/acl.conf.

5

Hello.

Please how i can do find a substring in the “where” for the condition. For example I have:

A payload = ’ this sample of the string"

I ned:

SELECT * FROM ‘t/#’ WHERE ‘sample’ in payload

Exist any sentence for a substring in one string…?

Thanks
Fausto.

6

You can using the following SQL:

SELECT *
FROM
  "t/#"
WHERE
  find(payload, 'example') != ''

By the way, If it’s a different question, it’s best to ask it in a separate post.