Created helloworld tutorial outline

cpp/helloworld/README.md

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+# gRPC C++ Hello World Tutorial
+
+### Install gRPC
+Make sure you have installed gRPC on your system. Follow the instructions here:
+[https://github.com/grpc/grpc/blob/master/INSTALL](https://github.com/grpc/grpc/blob/master/INSTALL).
+
+### Get the tutorial source code
+
+The example code for this and our other examples lives in the `grpc-common`
+GitHub repository. Clone this repository to your local machine by running the
+following command:
+
+
+```sh
+$ git clone https://github.com/google/grpc-common.git
+```
+
+Change your current directory to grpc-common/cpp/helloworld
+
+```sh
+$ cd grpc-common/cpp/helloworld/
+```
+
+### Defining a service
+
+The first step in creating our example is to define a *service*: an RPC
+service specifies the methods that can be called remotely with their parameters
+and return types. As you saw in the
+[overview](#protocolbuffers) above, gRPC does this using [protocol
+buffers](https://developers.google.com/protocol-buffers/docs/overview). We
+use the protocol buffers interface definition language (IDL) to define our
+service methods, and define the parameters and return
+types as protocol buffer message types. Both the client and the
+server use interface code generated from the service definition.
+
+Here's our example service definition, defined using protocol buffers IDL in
+[helloworld.proto](https://github.com/grpc/grpc-common/blob/master/protos/helloworld.proto). The `Greeting`
+service has one method, `hello`, that lets the server receive a single
+`HelloRequest`
+message from the remote client containing the user's name, then send back
+a greeting in a single `HelloReply`. This is the simplest type of RPC you
+can specify in gRPC - we'll look at some other types later in this document.
+
+```
+syntax = "proto3";
+
+option java_package = "ex.grpc";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}
+
+```
+
+<a name="generating"></a>
+### Generating gRPC code
+
+Once we've defined our service, we use the protocol buffer compiler
+`protoc` to generate the special client and server code we need to create
+our application. The generated code contains both stub code for clients to
+use and an abstract interface for servers to implement, both with the method
+defined in our `Greeting` service.
+
+To generate the client and server side interfaces:
+
+```sh
+$ make helloworld.pb.cc
+```
+Which internally invokes the proto-compiler as:
+
+```sh
+$protoc -I ../../protos/ --cpp_out=. --grpc_out=. --plugin=protoc-gen-grpc=grpc_cpp_plugin helloworld.proto
+```
+
+### Writing a client
+
+This is an incomplete tutorial. For now the reader should refer to [greeter_client.cc](https://github.com/grpc/grpc-common/blob/master/cpp/helloworld/greeter_client.cc).
+
+### Writing a server
+
+This is an incomplete tutorial. For now the reader should refer to [greeter_server.cc](https://github.com/grpc/grpc-common/blob/master/cpp/helloworld/greeter_server.cc).