Multiple bi-directional gRPC calls over single pre-established TCP connection
<p>Is it possible to use <a href="http://www.grpc.io/" rel="nofollow">gRPC</a> such that all calls between two remote hosts
use a TCP connection that is established outside of gRPC? I would also like
to determine whether this TCP connection can be multiplexed for more than
one gRPC call, that the calls may be in either directions, and that gRPC
not close the socket.</p>

<p>The intent is to be able to use gRPC when two ends of gRPC are across a
firewall. The firewall only allows establishing a single TCP connection
that is initiated from within the firewall.</p>

<p>For the requirements only C++ and Java implementations may be on either side.</p>