WiFiClient.write blocks intermittently about arduino-pico

[earlephilhower]

5 seconds is the internal timeout, so something somewhere is timing out. Unfortunately without an MCVE there's not much anyone but yourself can do.

There is a limited packet space present in the LWIP implementation (it needs to preallocate things since it runs in IRQ-level). You could try doubling it from 16k to 32k in lwipopts.h and rebuilding libpico.a and re-running your full app. If you're unable to rebuild and would like me to get you a test version of libpico.a, let me know.

[obdevel]

Thanks. I have discovered the availableForWrite() method which should allow me to preempt this and back off. Initial testing shows it works mostly, with only one instance so far where it reported space but the write still failed.

At this stage, I'm trying to find the limits of capacity and throughput so I can set reasonable expectations. I may take up your kind offer but I also need to consider other people in my group who may want to use this code. Requiring them to patch the core would not be ideal.

I will also try to create an MCVE but even in reduced form it would be fairly large. And it would require multiple Picos, although for load testing I have a program running on my Mac.

[obdevel]

I have been experimenting with UDP broadcasts as an alternative to writing the same data to multiple client TCP sockets. It works well and gets around the buffer starvation problem.

I have learned that the iPhone personal hotspot doesn't support UDP broadcasts ... sigh. All useful knowledge.

I'll close this issue and reopen if required. Thanks again.