ESP8266, NodeMcu and MQTT: Event subscription load testing

I’ve being doing some testing with the latest NodeMcu regarding MQTT support. My experience is, more or less, documented here: .

I wanted to check if concurrent subscription seems to work fine, since I know that publishing is not straightforward. In the code from the above link, the esp8266 subscribes to four topics, named topic1, topic2 and so on.

This simple bash script, calls repeatedly the mosquitto broker publishing command:

for i in {1..60}
/home/pcortex/01.Develop/mosquitto/mosquitto-1.3.5/client/mosquitto_pub -h -m "Mensagem $i" -t topic1
/home/pcortex/01.Develop/mosquitto/mosquitto-1.3.5/client/mosquitto_pub -h -m "Mensagem $i" -t topic2

But with low values on the loop count, the MQTT code on the esp8266 seems to work fine, but with higher values, as above (60), the esp8266 hangs and reboots. One interesting thing was that after some testing not even doing a reset or completely powering it off, I was able to bring the esp8266 back online. It just put out garbage on the serial output and that was it. Strange indeed.

So I’ve reflash it again with the latest NodeMcu version (lots of reflashing hey 🙂 ), but still the esp8266 did not recover! Only garbage out when connecting to the serial port (And no, it wasn’t the serial port rate issue). So I’ve reflashed again the original AT Firmware, and it came back to life again, and then reflash it again with the latest Nodemcu version.

Adding a delay on the bash script, before the done line, like sleep 1 seems to keep the esp8266 running without issue.

So indeed this shows, that bombarding the esp8266 with MQTT messages in burst mode is not a good idea…


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