Some clients can't connect to our server.

[Bengt Gustafsson]

Hi. We have a gRPC based server on the internet and our own client software connecting to it at different customer sites. Quite often these clients can't connect due to probably some firewall issue in their intranet to internet connection. We changed to using port 443 to avoid firewalls blocking outgoing traffic on unknown ports but that doesn't help.

I turned on logging using gpr_set_log_verbosity(GPR_LOG_SEVERITY_INFO); but I got nothing at all before I got the return value deadline_exceeded. I have increased the timeout to 10s so it's not just slow.

I replaced the URL with the corresponding ip number and then I got could not connect to all addresses with no measurable delay.

Any tips and tricks that could be useful?

[Bengt Gustafsson]

We were thinking that maybe the problem is that the gRPC library is trying to use a http proxy set up by our customers' IT administrators on employee PCs. To me it is not clear whether gRPC (C++ version, out of the box) would try to use proxy settings in a PC if there are any.

One customer tried a laptop at home which worked, brought it to the office, and it couldn connect anymore.

[yas...@google.com]

That is probably the issue that you are running into. Please refer - https://github.com/grpc/grpc/blob/master/doc/environment_variables.md for the environment variables that gRPC uses. You can override by using the channel arg - GRPC_ARG_ENABLE_HTTP_PROXY and setting it to 0.