1 /*
2 *
3 * Copyright 2015 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 <iostream>
20 #include <memory>
21 #include <string>
22
23 #include <grpcpp/grpcpp.h>
24 #include <grpc/support/log.h>
25
26 #include "helloworld.grpc.pb.h"
27
28 using grpc::Channel;
29 using grpc::ClientAsyncResponseReader;
30 using grpc::ClientContext;
31 using grpc::CompletionQueue;
32 using grpc::Status;
33 using helloworld::HelloRequest;
34 using helloworld::HelloReply;
35 using helloworld::Greeter;
36
37 class GreeterClient {
38 public:
GreeterClient(std::shared_ptr<Channel> channel)39 explicit GreeterClient(std::shared_ptr<Channel> channel)
40 : stub_(Greeter::NewStub(channel)) {}
41
42 // Assembles the client's payload, sends it and presents the response back
43 // from the server.
SayHello(const std::string & user)44 std::string SayHello(const std::string& user) {
45 // Data we are sending to the server.
46 HelloRequest request;
47 request.set_name(user);
48
49 // Container for the data we expect from the server.
50 HelloReply reply;
51
52 // Context for the client. It could be used to convey extra information to
53 // the server and/or tweak certain RPC behaviors.
54 ClientContext context;
55
56 // The producer-consumer queue we use to communicate asynchronously with the
57 // gRPC runtime.
58 CompletionQueue cq;
59
60 // Storage for the status of the RPC upon completion.
61 Status status;
62
63 // stub_->PrepareAsyncSayHello() creates an RPC object, returning
64 // an instance to store in "call" but does not actually start the RPC
65 // Because we are using the asynchronous API, we need to hold on to
66 // the "call" instance in order to get updates on the ongoing RPC.
67 std::unique_ptr<ClientAsyncResponseReader<HelloReply> > rpc(
68 stub_->PrepareAsyncSayHello(&context, request, &cq));
69
70 // StartCall initiates the RPC call
71 rpc->StartCall();
72
73 // Request that, upon completion of the RPC, "reply" be updated with the
74 // server's response; "status" with the indication of whether the operation
75 // was successful. Tag the request with the integer 1.
76 rpc->Finish(&reply, &status, (void*)1);
77 void* got_tag;
78 bool ok = false;
79 // Block until the next result is available in the completion queue "cq".
80 // The return value of Next should always be checked. This return value
81 // tells us whether there is any kind of event or the cq_ is shutting down.
82 GPR_ASSERT(cq.Next(&got_tag, &ok));
83
84 // Verify that the result from "cq" corresponds, by its tag, our previous
85 // request.
86 GPR_ASSERT(got_tag == (void*)1);
87 // ... and that the request was completed successfully. Note that "ok"
88 // corresponds solely to the request for updates introduced by Finish().
89 GPR_ASSERT(ok);
90
91 // Act upon the status of the actual RPC.
92 if (status.ok()) {
93 return reply.message();
94 } else {
95 return "RPC failed";
96 }
97 }
98
99 private:
100 // Out of the passed in Channel comes the stub, stored here, our view of the
101 // server's exposed services.
102 std::unique_ptr<Greeter::Stub> stub_;
103 };
104
main(int argc,char ** argv)105 int main(int argc, char** argv) {
106 // Instantiate the client. It requires a channel, out of which the actual RPCs
107 // are created. This channel models a connection to an endpoint (in this case,
108 // localhost at port 50051). We indicate that the channel isn't authenticated
109 // (use of InsecureChannelCredentials()).
110 GreeterClient greeter(grpc::CreateChannel(
111 "localhost:50051", grpc::InsecureChannelCredentials()));
112 std::string user("world");
113 std::string reply = greeter.SayHello(user); // The actual RPC call!
114 std::cout << "Greeter received: " << reply << std::endl;
115
116 return 0;
117 }
118