Darwin push port - overnight data

[belcher...@googlemail.com]

I've got a PHP implementation using https://github.com/stomp-php/stomp-php to connect to and process data from the darwin push port feed. As part of my code, I keep track of both when I last attempted to read data and also the latency between a message's time and when I processed it.

Overnight (pretty consistently) I am getting a spell, often around 2/3am, where my system is showing as not having attempted to read data. This then comes back up with a low latency.

My assumption is that Darwin has no data to send me, but that stomp php is continuing to read data even when there is nothing to read and so because it never receives an end of message it never returns to my code for me to track that we have attempted.

The developers of stomp php have suggested that Darwin may be sending NULL bytes to keep the connection open which results in it holding off on returning with no data to read.

Does anyone know what Darwin does when it has no data? I am not sending a heartbeat header as I think that would trigger the same scenario.