Problem: reimplemented zmq_proxy_steerable control socket type is not
backwards compatible - replies are always sent.
In the past, zmq_proxy_steerable never sent a reply for
commands that weren't STATISTICS, so only really worked with PAIR and didn't
work at all with REP. Now it only supports REP and PAIR semantics changed. This
breaks compatibility with PAIR in a subtle and slightly annoying way if
HWMs are hit without reading the replies.
Solution: Add a check to send the empty reply only for
REP control sockets. This restores backwards compatibility, and supports
REP, PAIR, and SUB (for non-reply commands).
I had no knowledge of the pre-MPL-2.0 implementation. This fix is based
on docs and prior API usage. I contribute this under MPL-2.0.
It is contriubted under the MPL-2.0.
I had no knowledge of the previous implementation of zmq_proxy_steerable().
This version was developed based on expectations set in the old man page with one exception. This version uses a REP/REQ for the proxy control protocol sockets. The old man page example used PUB/SUB which is nonsensical given the STATISTICS command requires two way communication.
Solution: remove implementation. Laurent Alebarde <l.alebarde@free.fr>,
the author, did not respond to requests to allow relicensing to MPL2,
so we have to remove his copyrighted work.
Make the API into an empty stub that returns -EOPNOTSUPP.
