Problems with usocket implementations in micropython?

Other & Legacy Products
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1

Hello,

I noticed that when we try to connect to the wrong IP with a socket, a strange and incorrect behavior occurs. If we immediately try a connection to a correct IP, we fail to connect, only the third or fourth time we manage to connect.

I use XBXC3 module, Cellular modem, XBC LTE-M / NB-IoT Global, with firmware 11415.
I used the micropython language to send text messages to an MQTT server.
For this I used the umqtt.simple library.

In the attached source code, there are 2 functions: wait_modem_to_connect waiting to connect to the NB-IoT network and the publish_to_mqtt function sending a text message to the server.

In the main program (while loop) the message publishing function is called 4 times.
I used Mosquitto as a test server. Intentionally a second time the server’s IP is wrong.

It is noticed that the timeout error (wrong IP) appears a second time, that is correct.
BUT, this happens for the third time for the next connection, and that is not correct, because here is a correct IP.
This is always the same and does not depend on the state of the server.

I didn’t notice anything in the library code that could fix this behavior.

The question is: do you think it is from the umqtt.simple class or is it a malfunction / possible error in the implementation of the socket / usocket class in the micropython language of the Cellular Xbee module?

The source code and capture is bellow:

MicroPython v1.11-1417-g4092c08 on 2020-02-12; XBC LTE-M/NB-IoT Global with EFR32MG
Type “help()” for more information.
>>>
flash compile mode; Ctrl-C to cancel, Ctrl-D to finish
1^^^ # import modules
2^^^ from umqtt.simple import MQTTClient
3^^^ import network
4^^^ import time
5^^^ import xbee
6^^^
7^^^ # here we start the main program
8^^^ print(“Start program …”)
9^^^ x = xbee.XBee()
10^^^ x.atcmd(‘SM’, 0)
11^^^
12^^^ def wait_modem_to_connect():
13^^^ c = network.Cellular()
14^^^ while not c.isconnected():
15^^^ print(“wait to connect …”)
16^^^ time.sleep(2)
17^^^ print(str(c.ifconfig()))
18^^^
19^^^ def publish_to_mqtt(server, port, topic, message):
20^^^ try:
21^^^ print(“Connect to the MQTT server (” + str(server) + “) …”)
22^^^ mqttClient = MQTTClient(“CLIENT_TEST”, server, port)
23^^^ mqttClient.connect()
24^^^ print(“MQTT server connected”)
25^^^ mqttClient.publish(topic, message, True, 1)
26^^^ mqttClient.disconnect()
27^^^ print(str(message) + " is publish")
28^^^ except Exception as err:
29^^^ print(str(err))
30^^^
31^^^ while True:
32^^^ # wait to connect to NB-IoT
33^^^ wait_modem_to_connect()
34^^^ # publish 4 messages for four times
35^^^ publish_to_mqtt(“5.196.95.208”, 1883, “TEST_MQTT_DIGI 1”, “Message 1”)
36^^^ publish_to_mqtt(“5.196.95.207”, 1883, “TEST_MQTT_DIGI 2”, “Message 2”)
37^^^ publish_to_mqtt(“5.196.95.208”, 1883, “TEST_MQTT_DIGI 3”, “Message 3”)
38^^^ publish_to_mqtt(“5.196.95.208”, 1883, “TEST_MQTT_DIGI 4”, “Message 4”)
39^^^
40^^^ time.sleep(120)
Erasing /flash/main.mpy…
Compiling 1240 bytes of code…
Saved compiled code to /flash/main.mpy (868 bytes).
Automatically run this code at startup [Y/n]? Y
Stored code will run at startup.
Press CTRL-R in the REPL to run the code at any time.

MicroPython v1.11-1417-g4092c08 on 2020-02-12; XBC LTE-M/NB-IoT Global with EFR32MG
Type “help()” for more information.
>>>
Loading /flash/main.mpy…
Running bytecode…
Start program …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
wait to connect …
(‘10.21.0.141’, ‘255.255.255.255’, ‘0.0.0.0’, ‘0.0.0.0’)
Connect to the MQTT server (5.196.95.208) …
MQTT server connected
Message 1 is publish
Connect to the MQTT server (5.196.95.207) …
[Errno 7110] ETIMEDOUT
Connect to the MQTT server (5.196.95.208) …
[Errno 7110] ETIMEDOUT
Connect to the MQTT server (5.196.95.208) …
MQTT server connected
Message 4 is publish
(‘10.21.0.141’, ‘255.255.255.255’, ‘0.0.0.0’, ‘0.0.0.0’)
Connect to the MQTT server (5.196.95.208) …
MQTT server connected
Message 1 is publish
Connect to the MQTT server (5.196.95.207) …
[Errno 7110] ETIMEDOUT
Connect to the MQTT server (5.196.95.208) …
[Errno 7110] ETIMEDOUT
Connect to the MQTT server (5.196.95.208) …
MQTT server connected
Message 4 is publish
Traceback (most recent call last):
File “”, line 40, in
KeyboardInterrupt:

MicroPython v1.11-1417-g4092c08 on 2020-02-12; XBC LTE-M/NB-IoT Global with EFR32MG
Type “help()” for more information.
>>>

Thank you,
Ionel

2

Dragomi,

I would suggest using the socket close function

https://www.digi.com/resources/documentation/Digidocs/90002258/#reference/r_frame_socket_0x43.htm%3FTocPath%3DAPI%2520frames|_____21

https://www.digi.com/resources/documentation/digidocs/90002219/default.htm#tasks/t_basic_socket.htm?Highlight=closing%20sockets

This way it will close the undesired socket before you move on to the next one.

3

Hello, mvut,

I’m trying to force the socket.close () function.
But the behavior is the same.
In fact, I think, because the IP is wrong, the socket fails to connect, so socket.close () does not help.

If you have any other idea I would appreciate it.
Thanks,
Ionel

20^^^ try:
21^^^ print(“Connect to the MQTT server (” + str(server) + “) …”)
22^^^ mqttClient = MQTTClient(“CLIENT_TEST”, server, port)
23^^^ mqttClient.connect()
24^^^ print(“MQTT server connected”)
25^^^ mqttClient.publish(topic, message, True, 1)
26^^^ print(str(message) + " is publish")
27^^^ except Exception as err:
28^^^ print(str(err))
29^^^
30^^^ try:
31^^^ mqttClient.disconnect()
32^^^ except Exception as err:
33^^^ print(str(err))