HttpClient times out on first request after some idle time

[ScruffR]

@turbo2ltr

Can you explain a bit why you set up your while() that way?

There is a great explanation about this over here

Millis() and rollover tutorial

The millis() function is handy for timing things with the Particle Photon (and Electron, and Core). It executes very quickly and has a good resolution (milliseconds). From the manual: Returns the number of milliseconds since the device began running the current program. This number will overflow (go back to zero), after approximately 49 days. Note: The return value for millis is an unsigned long, errors may be generated if a programmer tries to do math with other datatypes such as ints. Now…

BTW

@turbo2ltr

the photon is "breathing" blue.

Do you mean breathing cyan, blue would indicate an issue

But looking into the HTTPClient lib, this seems to be part of your troubles

static const uint16_t TIMEOUT = 5000; // Allow maximum 5s between data packets.