EMQPUBOPEN – create a publish message topic

Create and view publish message topics. Use these topics to publish data to things in the cloud.

The topic name depends on the MQTT parameter unless you use a token. See Using the AnyNet SMARTconnect™ configuration file.

You can use the following tokens to construct the topic name:

• $t — Returns the cloud thingName.
• $i — Returns the device International Mobile Equipment Identity (IMEI).

For example, status/$i publishes as status/.

You can only include one token in a topic.

Type	Syntax	Response
Test	AT+EMQPUBOPEN=?	+EMQPUBOPEN: (0-7) and OK
Read	AT+EMQPUBOPEN?	A list of publish topics and OK
Write	AT+EMQPUBOPEN=(0-7),"/[$t | $i]"	Creates or updates a publish topic

The Read command returns topics in this format:

0: /<[mqtt] topicsuffix>
1: /<[mqtt] topicsuffix>
OK

The returned topic list includes:

• An index number, starting at 0.
• The unique publish topic name for the index.
• The appended topicsuffix path.

topicsuffix can include $i for the IMEI or $t for the cloud thingName. The maximum $t length is 128 characters for AWS and 255 characters for Google. The complete topic must not exceed the MQTT broker limit of 256 characters. The Quectel module does not return empty topics.

For the Write command:

• Set the publish index from 0 through 7.
• Set a publish topic title up to 256 characters, including /cloudThingName or /IMEI.
• Do not use special characters in a topic title.
• Optionally include $t or $i.

Examples

Create a topic with the IMEI token:

AT+EMQPUBOPEN=0,"PublishToCloud0/$i"
OK
+EMQPUBOPEN: 0,0

Create a topic without a token:

AT+EMQPUBOPEN=1,"PublishToCloud1"
OK
+EMQPUBOPEN: 1,0

List publish topics:

AT+EMQPUBOPEN?
0: PublishToCloud0/862061040777777
1: PublishToCloud1/AWSthingName
OK

Publish a JSON message:

AT+EMQPUBLISH=0,1,"{"imei":"$i","user":"1","sys":"128","dia":"112","pul":"075","ano":"0","time":"2023/11/30,20:10:12-20","ver":"BP01\_2.0","devdata":{"r":$r,"rat":"$a","mcc":$c,"mnc":$n,"imsi":$s,"batt":87\}}"
OK
:SEND OK

In the last example, the MQTT broker receives:

{
  "imei": "867730056224474",
  "user": "1",
  "sys": "128",
  "dia": "112",
  "pul": "075",
  "ano": "0",
  "time": "2023/11/30,20:10:12-20",
  "ver": "BP01_2.0",
  "devdata": {
    "r": -68,
    "rat": "eMTC",
    "mcc": 310,
    "mnc": 230,
    "imsi": 302760007540320,
    "batt": 87
  }
}

For useful AWS information regarding maximum lengths, see: AWS IoT Core endpoints and quotas.