The Echo Xcode project contains a Mac app that can be used to instantiate and run local gRPC clients and servers. It depends on the gRPC Xcode project, which requires a local build of the gRPC Core C library. To build that, please run "make" in the root of your gRPC distribution. Next use Xcode's "Add Files..." command to add the SwiftGRPC.xcodeproj to your project and then add the CzLib, gRPC, CgRPC, and BoringSSL libraries to the target dependencies of "Echo".