| [](https://cocoapods.org/pods/gRPC) |
| # gRPC Objective-C with CFStream |
| |
| gRPC now provides the option to use Apple's CFStream API (rather than TCP |
| sockets) for networking. Using CFStream resolves a bunch of network connectivity transition issues |
| (see the [doc](https://github.com/grpc/grpc/blob/master/src/objective-c/NetworkTransitionBehavior.md) |
| for more information). |
| |
| <s>CFStream integration is now in experimental state. You will need explicit opt-in to use it to get |
| the benefits of resolving the issues above. We expect to make CFStream the default networking |
| interface that gRPC uses when it is ready for production.</s> |
| |
| As of v1.21.0, CFStream integration is now the default networking stack being used by gRPC |
| Objective-C on iOS layer. You get to use it automatically without special configuration needed. See |
| below on how to disable CFStream in case of problem. |
| |
| As of v1.23.0, CFStream is enabled by default on iOS for all wrapped languages. See below on how to |
| disable CFStream in case of a problem. |
| |
| ## Usage |
| If you use gRPC on iOS, CFStream is on automatically. If you use it on other |
| platforms, you can turn it on with macro `GRPC_CFSTREAM=1` for the pod 'gRPC-Core' and 'gRPC'. In |
| case of problem and you want to disable CFStream on iOS, you can set environment variable |
| "grpc\_cfstream=0". |
| |
| ## Caveats |
| It is known to us that the CFStream API has some bug (FB6162039) which will cause gRPC's CFStream |
| networking layer to stall occasionally. The issue mostly occur on MacOS systems (including iOS |
| simulators on MacOS); iOS may be affected too but we have not seen issue there. gRPC provides a |
| workaround to this problem with an alternative poller based on CFRunLoop. The poller can be enabled |
| by setting environment variable `GRPC_CFSTREAM_RUN_LOOP=1`. Note that the poller is a client side |
| only poller that does not support running a server on it. That means if an app opts in to the |
| CFRunLoop-based poller, the app cannot host a gRPC server (gRPC Objective-C does not support running |
| a server but other languages running on iOS do support it). |
| |
| ## Notes |
| |
| - Currently we do not support platforms other than iOS, although it is likely that this integration |
| can run on MacOS targets with Apple's compiler. |
| - Let us know if you meet any issue by filing issue and ping @stanleycheung. |
