FAQ of NB-IoT-protocol related questions
1.Understanding of resource Update report of the platform
2.The device can still send data to the platform after the device is deleted by the platform?
3.The platform shows it has received the device notice, but it shows the device doesn’t exist.
4.Can the device report data after it’s off line?
6.What is the maximum value of lifetime? Generally, what is its rational length?
7.Why the device is in an offline state on OneNET portal page?
9.The Integer/Float/string data uploaded are shown in the format of [10 100, 123].
10.What is the format for data report from read to resource and from read to instance respectively?
13.Will the device receive a reply when it sends Con message to the platform?
| Relevant questions about data report, update and notification |
1.Understanding of resource Update report of the platform
Answer: When the access machine receives the Update message of the device, it will update the device lifetime; then it will compare the object instance included in Linkobject in the update with the last resource, eliminate the old object instance included in the former resource and not included in Update, and cancel the corresponding subscription; then it will add the new object instance in update, and release the device registration operation to the new object instance (Observer, Discover). (Observer、discover)
2.The device can still send data to the platform after the device is deleted by the platform?
Answer: No. Because the platform keeps the caching information of device registration, the following state may exist: After the online device is deleted, it can still send data to the platform, and can receive correct response. If the device lifetime is very long, within the lifetime, the device can report data.After sending the next update information, the platform will timely remove the device.
3.The platform shows it has received the device notice, but it shows the device doesn’t exist.
Answer: Maybe, it because the device is not timely updated, but the platform has already eliminated the device.
4.Can the device report data after it’s off line?
Answer: After the platform receives the data reported by the offline device, it will release Rst and prevent the device from reporting message again.
5.The device doesn’t report any message within the lifetime, but the platform still shows the device is online.
Answer: According to the mechanism for the platform to judge the offline state of the device, display of the online state of the device may be delayed for about one minute.
6.What is the maximum value of lifetime? Generally, what is its rational length?
Answer: The maximum value of a 32-bit module is 2^32-1 (s). The lifetime is set according to the device use.
- It can be set arbitrarily if the device won’t use the online command.
- If the device needs to use the online command, and the notification frequency is very low, it’s recommended to be less than 5min.
7.Why the device is in an offline state on OneNET portal page?
Answer: The device online status is only decided by whether the lifetime expires.
Lifetime is a parameter of device connection (Register), expressed in seconds; if it’s not specified, it’s 86400 by default. After the lifetime expires, the platform will kick the device off line. Then the device can’t report data and can only register again (Register). The device can prolong the lifetime by sending Register Update message before the lifetime expires.
8.The data are uploaded successively, but only one data is stored to the platform every five minutes?
Answer: Coap protocol can filter repeated messages through Message id and Token. For notified packet, if the subscription pathway is the same, the Token will be the same. If Message id is not changed, the message will be considered a repeated one and filtered. The time window for filtration of repeated messages is 247 seconds, namely, after the first message is processed, the messages repeated within 247 seconds will be filtered.
9.The Integer/Float/string data uploaded are shown in the format of [10, 100, 123]?
Answer: There is no standard resource model defined using IPSO. For non-IPSO model Object ID and Resource ID, the platform can’t judge the data type of the resource, and will process the message according to the binary system.
| Relevant questions about reading | writing | execution, API, cache command |
10.What is the format for data report from read to resource and from read to instance respectively?
Answer: From Read to Resource, the report format is Plain/Text; from Read to Instance, the report format is Tlv.
11.The platform releases a command to the device; before the device is notified, the device receives Acsii code, but after the device reports, it can correctly receive data.
Answer: This is because the module doesn’t know about the resource type. When the device notifies the platform, the module declares the resource type, and after it receives the writing command of corresponding resources from the platform, it can correctly translate the resource type, and then correctly receive the data. When the resource type is unknown, the module will take the resource as Opaque type, so Ascii code will be displayed.
12.Why there is timeout when data are released, but there will be no timeout if there is data interaction?
Answer: If there are no uplink data for a long time, the core network will kick off the linkage information cached before; the route can’t find the device, thus causing timeout.
13.Will the device receive a reply when it sends Con message to the platform?
Answer: After receiving Con message, the access machine will reply to Ack; the normal message will be processed according to the normal flow; for abnormal Con message, the access machine will discard the message, but it will also release Ack or Rst.