in my POAs logs I see messages like this:

Http Client Call /gwcal/poamsg?action=User.List.update&po.ip=<ip>:<port> to
gw_cal resulted with rc = [8912]

Most of them are with "rc = 0", but recurring there are quite a few with

8912 seems to be a TCP/IP communication problem - but I don't understand
between which partners: between Client and Calendar Publishing Host or
between the latter and the POA? Since it is the POA's log file I guess it's
the communication to the POA, but that "Http Client Call" bothers me. Of
course the Calendar Publishing Host can be a client to the POA - is it that
what is meant here? Or is there communication initiated from the POA as a
client to the Calendar Publishing Host?

I wasn't able to reproduce an of those messages, when accessing published
calendars - what action does trigger them?