1 /*
2 *
3 * Copyright 2021 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #include <condition_variable>
20 #include <iostream>
21 #include <memory>
22 #include <mutex>
23 #include <string>
24
25 #include "absl/flags/flag.h"
26 #include "absl/flags/parse.h"
27
28 #include <grpcpp/grpcpp.h>
29
30 #ifdef BAZEL_BUILD
31 #include "examples/protos/helloworld.grpc.pb.h"
32 #else
33 #include "helloworld.grpc.pb.h"
34 #endif
35
36 ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
37
38 using grpc::Channel;
39 using grpc::ClientContext;
40 using grpc::Status;
41 using helloworld::Greeter;
42 using helloworld::HelloReply;
43 using helloworld::HelloRequest;
44
45 class GreeterClient {
46 public:
GreeterClient(std::shared_ptr<Channel> channel)47 GreeterClient(std::shared_ptr<Channel> channel)
48 : stub_(Greeter::NewStub(channel)) {}
49
50 // Assembles the client's payload, sends it and presents the response back
51 // from the server.
SayHello(const std::string & user)52 std::string SayHello(const std::string& user) {
53 // Data we are sending to the server.
54 HelloRequest request;
55 request.set_name(user);
56
57 // Container for the data we expect from the server.
58 HelloReply reply;
59
60 // Context for the client. It could be used to convey extra information to
61 // the server and/or tweak certain RPC behaviors.
62 ClientContext context;
63
64 // The actual RPC.
65 std::mutex mu;
66 std::condition_variable cv;
67 bool done = false;
68 Status status;
69 stub_->async()->SayHello(&context, &request, &reply,
70 [&mu, &cv, &done, &status](Status s) {
71 status = std::move(s);
72 std::lock_guard<std::mutex> lock(mu);
73 done = true;
74 cv.notify_one();
75 });
76
77 std::unique_lock<std::mutex> lock(mu);
78 while (!done) {
79 cv.wait(lock);
80 }
81
82 // Act upon its status.
83 if (status.ok()) {
84 return reply.message();
85 } else {
86 std::cout << status.error_code() << ": " << status.error_message()
87 << std::endl;
88 return "RPC failed";
89 }
90 }
91
92 private:
93 std::unique_ptr<Greeter::Stub> stub_;
94 };
95
main(int argc,char ** argv)96 int main(int argc, char** argv) {
97 absl::ParseCommandLine(argc, argv);
98 // Instantiate the client. It requires a channel, out of which the actual RPCs
99 // are created. This channel models a connection to an endpoint specified by
100 // the argument "--target=" which is the only expected argument.
101 std::string target_str = absl::GetFlag(FLAGS_target);
102 // We indicate that the channel isn't authenticated (use of
103 // InsecureChannelCredentials()).
104 GreeterClient greeter(
105 grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
106 std::string user("world");
107 std::string reply = greeter.SayHello(user);
108 std::cout << "Greeter received: " << reply << std::endl;
109
110 return 0;
111 }
112