1 Topic by bettylim (edited by bettylim 2025-10-08 01:51:48)

  • Registered: 2025-10-05
  • Posts: 2

Topic: WolfMQTT Slows Down on Limited Hardware

I’m using WolfMQTT on a low-memory embedded system and having a hard time optimizing its performance. When sending or receiving larger payloads, the device often slows down or even disconnects. I’ve tried tweaking buffer sizes, QoS levels, and keep-alive settings, but nothing seems to fully stabilize it.

I’ve been studying the examples from the official GitHub repo:
https://github.com/wolfSSL/wolfMQTT slope game

They’re helpful, but I’m still struggling to find the right balance between memory usage and speed on constrained hardware.

Has anyone else faced similar issues with WolfMQTT on small systems?

What buffer sizes or memory management techniques worked best for you?

Does lowering QoS actually improve stability in low-memory setups?

Any specific code tweaks or configuration tricks that made a big difference?

Thanks in advance!

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  • From: Mobile, AL
  • Registered: 2013-12-11
  • Posts: 377

Re: WolfMQTT Slows Down on Limited Hardware

Hi bettylim

Welcome to the wolfSSL forums.

Are you using TLS? Which TCP stack are you using? wolfMQTT does not consume much in the way of resources.

Higher QoS increases the number of round trips required, but does not increase memory usage significantly.

The buffer sizes used should correlate with the average data payload size to optimize memory use. For large payloads, it would be optimal to set it to the TCP driver buffer size.

It would be helpful to discuss your specific project in more detail. Feel free to open a support ticket by emailing support@wolfssl.com

Thanks,
Eric - wolfSSL Support

embhorn's Website

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  • Registered: 2025-10-05
  • Posts: 2

Re: WolfMQTT Slows Down on Limited Hardware

Hi embhorn,

Thanks for the quick reply and the clarification.

Yes, I’m using TLS (wolfSSL) on top of the MQTT connection — that’s likely where most of the overhead comes from. The device runs on a lightweight custom TCP/IP stack (similar to lwIP, but trimmed down for our MCU).

I understand that WolfMQTT itself is quite efficient, but it seems the combination of TLS handshakes, message fragmentation, and limited heap memory (only around 64 KB total) might be contributing to the slowdown.

I’ll experiment with matching the MQTT buffer size to the TCP driver buffer as you suggested. Do you recommend keeping the MQTT buffer slightly smaller than the TCP buffer, or the same size?

Also, would using non-blocking sockets help reduce latency under tight memory constraints?

Best regards,
bettylim

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