gRPC是google开源的一套实现rpc调用的框架&＃xff0c;支持多种语言&＃xff0c;并且比较易用&＃xff0c;其数据传输是通过google自家的protobuf来序列化的&＃xff0c;下面我们通过改写gRPC的example来实现获取远程host内存的功能。

例子中的文件目录结构如下

./examples/cpp/sysproc
./examples/cpp/sysproc/sysproc_server.cc
./examples/cpp/sysproc/Makefile
./examples/protos/sysproc.proto


1.先定义protobuf文件

文件描述了接口的参数结构和接口结构
sysproc.proto

syntax &＃61; "proto3";service SysProcManager {rpc getSysProc (NullMessage) returns (SysProc) {}
}message NullMessage {}message SysProc {int32 memfree &＃61; 1;
};

由于这里的接口必须需要参数&＃xff0c;所以我们增加了一个Null类型的消息
我们定义了一个SysProc消息结构用于getSysProc rpc方法的返回值&＃xff0c;service的名字叫SysProcManager

服务器端代码

sysproc_service.cc

#include "sysproc.grpc.pb.h"
#include
#include
#include
#include
extern "C" {
#include
}using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;// Logic and data behind the server&＃39;s behavior.
class SysProcServiceImpl final : public SysProcManager::Service {Status getSysProc(ServerContext* context, const NullMessage* request,SysProc * reply) override {int memFree &＃61; 0;struct sysinfo info;sysinfo(&info);memFree &＃61; (int)(info.freeram);reply->set_memfree(memFree);return Status::OK;}
};void RunServer() {std::string server_address("0.0.0.0:50051");SysProcServiceImpl service;ServerBuilder builder;// Listen on the given address without any authentication mechanism.builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());// Register "service" as the instance through which we&＃39;ll communicate with// clients. In this case it corresponds to an *synchronous* service.builder.RegisterService(&service);// Finally assemble the server.std::unique_ptr server(builder.BuildAndStart());std::cout <<"Server listening on " <std::endl;// Wait for the server to shutdown. Note that some other thread must be// responsible for shutting down the server for this call to ever return.server->Wait();
}int main(int argc, char** argv) {RunServer();return 0;
}

SysProcServiceImpl先定义了一个Service类继承自我们刚刚定义的protobuf文件编译产生的grpc的文件SysProcManager::Service&＃xff0c;并实现getSysProc&＃xff0c;在后面的Makefile文件中会看到编译的过程
通过ServiceBuilder创建一个builder并监听服务器端口&＃xff0c;然后注册我们刚刚写的Service类&＃xff0c;这时候就wait处理客户端请求就好了

sysproc_client.cc

#include
#include
#include #include #include "sysproc.grpc.pb.h"using grpc::Channel;
using grpc::ClientContext;
using grpc::Status;class SysProcClient {public://创建客户端类&＃xff0c;该类通过一个SysProcManager&＃xff08;protobuf定义的Service&＃xff09;的stub来和服务器端进行通信SysProcClient(std::shared_ptr channel): stub_(SysProcManager::NewStub(channel)) {}// Assembles the client&＃39;s payload, sends it and presents the response back// from the server.int getSysProc() {// Data we are sending to the server.NullMessage request;// Container for the data we expect from the server.SysProc reply;// Context for the client. It could be used to convey extra information to// the server and/or tweak certain RPC behaviors.ClientContext context;// The actual RPC.//stub调用生成的接口调用serviceStatus status &＃61; stub_->getSysProc(&context, request, &reply);// Act upon its status.if (status.ok()) {return reply.memfree();} else {std::cout <": " <std::endl;return -1;}}private:std::unique_ptr stub_;
};int main(int argc, char** argv) {// Instantiate the client. It requires a channel, out of which the actual RPCs// are created. This channel models a connection to an endpoint (in this case,// localhost at port 50051). We indicate that the channel isn&＃39;t authenticated// (use of InsecureChannelCredentials()).//创建一个chanel用于定义一个和服务器端的网络连接&＃xff0c;传给client的stubSysProcClient sysproc_client(grpc::CreateChannel("localhost:50051", grpc::InsecureChannelCredentials()));int reply &＃61; sysproc_client.getSysProc();std::cout <<"Client received: " <std::endl;return 0;
}

Makefile:

HOST_SYSTEM &＃61; $(shell uname | cut -f 1 -d_)
SYSTEM ?&＃61; $(HOST_SYSTEM)
CXX &＃61; g&＃43;&＃43;
CPPFLAGS &＃43;&＃61; &＃96;pkg-config --cflags protobuf grpc&＃96;
CXXFLAGS &＃43;&＃61; -std&＃61;c&＃43;&＃43;11
ifeq ($(SYSTEM),Darwin)
LDFLAGS &＃43;&＃61; -L/usr/local/lib &＃96;pkg-config --libs protobuf grpc&＃43;&＃43; grpc&＃96;\-lgrpc&＃43;&＃43;_reflection\-ldl
else
LDFLAGS &＃43;&＃61; -L/usr/local/lib &＃96;pkg-config --libs protobuf grpc&＃43;&＃43; grpc&＃96;\-Wl,--no-as-needed -lgrpc&＃43;&＃43;_reflection -Wl,--as-needed\-ldl
endif
PROTOC &＃61; protoc
GRPC_CPP_PLUGIN &＃61; grpc_cpp_plugin
GRPC_CPP_PLUGIN_PATH ?&＃61; &＃96;which $(GRPC_CPP_PLUGIN)&＃96;PROTOS_PATH &＃61; ../../protosvpath %.proto $(PROTOS_PATH)all: system-check sysproc_client sysproc_serversysproc_client: sysproc.pb.o sysproc.grpc.pb.o sysproc_client.o$(CXX) $^ $(LDFLAGS) -o $&＃64;sysproc_server: sysproc.pb.o sysproc.grpc.pb.o sysproc_server.o$(CXX) $^ $(LDFLAGS) -o $&＃64;.PRECIOUS: %.grpc.pb.cc
%.grpc.pb.cc: %.proto$(PROTOC) -I $(PROTOS_PATH) --grpc_out&＃61;. --plugin&＃61;protoc-gen-grpc&＃61;$(GRPC_CPP_PLUGIN_PATH) $<.PRECIOUS: %.pb.cc
%.pb.cc: %.proto$(PROTOC) -I $(PROTOS_PATH) --cpp_out&＃61;. $<clean:rm -f *.o *.pb.cc *.pb.h sysproc_client sysproc_server# The following is to test your system and ensure a smoother experience.
# They are by no means necessary to actually compile a grpc-enabled software.PROTOC_CMD &＃61; which $(PROTOC)
PROTOC_CHECK_CMD &＃61; $(PROTOC) --version | grep -q libprotoc.3
PLUGIN_CHECK_CMD &＃61; which $(GRPC_CPP_PLUGIN)
HAS_PROTOC &＃61; $(shell $(PROTOC_CMD) > /dev/null && echo true || echo false)
ifeq ($(HAS_PROTOC),true)
HAS_VALID_PROTOC &＃61; $(shell $(PROTOC_CHECK_CMD) 2> /dev/null && echo true || echo false)
endif
HAS_PLUGIN &＃61; $(shell $(PLUGIN_CHECK_CMD) > /dev/null && echo true || echo false)SYSTEM_OK &＃61; false
ifeq ($(HAS_VALID_PROTOC),true)
ifeq ($(HAS_PLUGIN),true)
SYSTEM_OK &＃61; true
endif
endifsystem-check:
ifneq ($(HAS_VALID_PROTOC),true)&＃64;echo " DEPENDENCY ERROR"&＃64;echo&＃64;echo "You don&＃39;t have protoc 3.0.0 installed in your path."&＃64;echo "Please install Google protocol buffers 3.0.0 and its compiler."&＃64;echo "You can find it here:"&＃64;echo&＃64;echo " https://github.com/google/protobuf/releases/tag/v3.0.0"&＃64;echo&＃64;echo "Here is what I get when trying to evaluate your version of protoc:"&＃64;echo-$(PROTOC) --version&＃64;echo&＃64;echo
endif
ifneq ($(HAS_PLUGIN),true)&＃64;echo " DEPENDENCY ERROR"&＃64;echo&＃64;echo "You don&＃39;t have the grpc c&＃43;&＃43; protobuf plugin installed in your path."&＃64;echo "Please install grpc. You can find it here:"&＃64;echo&＃64;echo " https://github.com/grpc/grpc"&＃64;echo&＃64;echo "Here is what I get when trying to detect if you have the plugin:"&＃64;echo-which $(GRPC_CPP_PLUGIN)&＃64;echo&＃64;echo
endif
ifneq ($(SYSTEM_OK),true)&＃64;false
endif

运行

先运行服务器sysproc_server&＃xff0c;再运行sysproc_client就能看到结果的