439 lines
15 KiB
Markdown
439 lines
15 KiB
Markdown
# Client usage
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Clients use RPC to interact with the wallet. A client may be implemented in any
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language directly supported by [gRPC](http://www.grpc.io/), languages capable of
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performing [FFI](https://en.wikipedia.org/wiki/Foreign_function_interface) with
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these, and languages that share a common runtime (e.g. Scala, Kotlin, and Ceylon
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for the JVM, F# for the CLR, etc.). Exact instructions differ slightly
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depending on the language being used, but the general process is the same for
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each. In short summary, to call RPC server methods, a client must:
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1. Generate client bindings specific for the [wallet RPC server API](./api.md)
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2. Import or include the gRPC dependency
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3. (Optional) Wrap the client bindings with application-specific types
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4. Open a gRPC channel using the wallet server's self-signed TLS certificate
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The only exception to these steps is if the client is being written in Go. In
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that case, the first step may be omitted by importing the bindings from
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lbcwallet itself.
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The rest of this document provides short examples of how to quickly get started
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by implementing a basic client that fetches the balance of the default account
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(account 0) from a testnet3 wallet listening on `localhost:19244` in several
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different languages:
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- [Client usage](#client-usage)
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- [Go](#go)
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- [C++](#c)
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- [C#](#c-1)
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- [Node.js](#nodejs)
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- [Python](#python)
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Unless otherwise stated under the language example, it is assumed that
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gRPC is already already installed. The gRPC installation procedure
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can vary greatly depending on the operating system being used and
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whether a gRPC source install is required. Follow the [gRPC install
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instructions](https://github.com/grpc/grpc/blob/master/INSTALL) if
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gRPC is not already installed. A full gRPC install also includes
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[Protocol Buffers](https://github.com/google/protobuf) (compiled with
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support for the proto3 language version), which contains the protoc
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tool and language plugins used to compile this project's `.proto`
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files to language-specific bindings.
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## Go
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The native gRPC library (gRPC Core) is not required for Go clients (a
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pure Go implementation is used instead) and no additional setup is
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required to generate Go bindings.
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```Go
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package main
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import (
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"fmt"
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"path/filepath"
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pb "github.com/lbryio/lbcwallet/rpc/walletrpc"
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"golang.org/x/net/context"
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"google.golang.org/grpc"
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"google.golang.org/grpc/credentials"
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btcutil "github.com/lbryio/lbcutil"
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)
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var certificateFile = filepath.Join(btcutil.AppDataDir("lbcwallet", false), "rpc.cert")
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func main() {
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creds, err := credentials.NewClientTLSFromFile(certificateFile, "localhost")
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if err != nil {
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fmt.Println(err)
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return
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}
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conn, err := grpc.Dial("localhost:19244", grpc.WithTransportCredentials(creds))
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if err != nil {
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fmt.Println(err)
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return
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}
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defer conn.Close()
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c := pb.NewWalletServiceClient(conn)
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balanceRequest := &pb.BalanceRequest{
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AccountNumber: 0,
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RequiredConfirmations: 1,
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}
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balanceResponse, err := c.Balance(context.Background(), balanceRequest)
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if err != nil {
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fmt.Println(err)
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return
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}
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fmt.Println("Spendable balance: ", btcutil.Amount(balanceResponse.Spendable))
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}
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```
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<a name="cpp"/>
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## C++
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**Note:** Protocol Buffers and gRPC require at least C++11. The example client
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is written using C++14.
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**Note:** The following instructions assume the client is being written on a
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Unix-like platform (with instructions using the `sh` shell and Unix-isms in the
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example source code) with a source gRPC install in `/usr/local`.
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First, generate the C++ language bindings by compiling the `.proto`:
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```bash
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$ protoc -I/path/to/lbcwallet/rpc --cpp_out=. --grpc_out=. \
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--plugin=protoc-gen-grpc=$(which grpc_cpp_plugin) \
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/path/to/lbcwallet/rpc/api.proto
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```
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Once the `.proto` file has been compiled, the example client can be completed.
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Note that the following code uses synchronous calls which will block the main
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thread on all gRPC IO.
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```C++
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// example.cc
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#include <unistd.h>
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#include <sys/types.h>
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#include <pwd.h>
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#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <string>
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#include <grpc++/grpc++.h>
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#include "api.grpc.pb.h"
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using namespace std::string_literals;
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struct NoHomeDirectoryException : std::exception {
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char const* what() const noexcept override {
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return "Failed to lookup home directory";
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}
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};
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auto read_file(std::string const& file_path) -> std::string {
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std::ifstream in{file_path};
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std::stringstream ss{};
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ss << in.rdbuf();
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return ss.str();
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}
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auto main() -> int {
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// Before the gRPC native library (gRPC Core) is lazily loaded and
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// initialized, an environment variable must be set so BoringSSL is
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// configured to use ECDSA TLS certificates (required by lbcwallet).
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setenv("GRPC_SSL_CIPHER_SUITES", "HIGH+ECDSA", 1);
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// Note: This path is operating system-dependent. This can be created
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// portably using boost::filesystem or the experimental filesystem class
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// expected to ship in C++17.
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auto wallet_tls_cert_file = []{
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auto pw = getpwuid(getuid());
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if (pw == nullptr || pw->pw_dir == nullptr) {
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throw NoHomeDirectoryException{};
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}
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return pw->pw_dir + "/.lbcwallet/rpc.cert"s;
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}();
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grpc::SslCredentialsOptions cred_options{
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.pem_root_certs = read_file(wallet_tls_cert_file),
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};
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auto creds = grpc::SslCredentials(cred_options);
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auto channel = grpc::CreateChannel("localhost:19244", creds);
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auto stub = walletrpc::WalletService::NewStub(channel);
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grpc::ClientContext context{};
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walletrpc::BalanceRequest request{};
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request.set_account_number(0);
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request.set_required_confirmations(1);
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walletrpc::BalanceResponse response{};
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auto status = stub->Balance(&context, request, &response);
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if (!status.ok()) {
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std::cout << status.error_message() << std::endl;
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} else {
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std::cout << "Spendable balance: " << response.spendable() << " Satoshis" << std::endl;
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}
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}
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```
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The example can then be built with the following commands:
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```bash
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$ c++ -std=c++14 -I/usr/local/include -pthread -c -o api.pb.o api.pb.cc
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$ c++ -std=c++14 -I/usr/local/include -pthread -c -o api.grpc.pb.o api.grpc.pb.cc
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$ c++ -std=c++14 -I/usr/local/include -pthread -c -o example.o example.cc
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$ c++ *.o -L/usr/local/lib -lgrpc++ -lgrpc -lgpr -lprotobuf -lpthread -ldl -o example
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```
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<a name="csharp"/>
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## C#
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The quickest way of generating client bindings in a Windows .NET environment is
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by using the protoc binary included in the gRPC NuGet package. From the NuGet
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package manager PowerShell console, this can be performed with:
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```
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PM> Install-Package Grpc
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```
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The protoc and C# plugin binaries can then be found in the packages directory.
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For example, `.\packages\Google.Protobuf.x.x.x\tools\protoc.exe` and
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`.\packages\Grpc.Tools.x.x.x\tools\grpc_csharp_plugin.exe`.
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When writing a client on other platforms (e.g. Mono on OS X), or when doing a
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full gRPC source install on Windows, protoc and the C# plugin must be installed
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by other means. Consult the [official documentation](https://github.com/grpc/grpc/blob/master/src/csharp/README.md)
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for these steps.
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Once protoc and the C# plugin have been obtained, client bindings can be
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generated. The following command generates the files `Api.cs` and `ApiGrpc.cs`
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in the `Example` project directory using the `Walletrpc` namespace:
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```PowerShell
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PS> & protoc.exe -I \Path\To\lbcwallet\rpc --csharp_out=Example --grpc_out=Example `
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--plugin=protoc-gen-grpc=\Path\To\grpc_csharp_plugin.exe `
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\Path\To\lbcwallet\rpc\api.proto
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```
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Once references have been added to the project for the `Google.Protobuf` and
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`Grpc.Core` assemblies, the example client can be implemented.
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```C#
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using Grpc.Core;
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using System;
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using System.IO;
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using System.Text;
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using System.Threading.Tasks;
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using Walletrpc;
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namespace Example
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{
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static class Program
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{
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static void Main(string[] args)
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{
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ExampleAsync().Wait();
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}
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static async Task ExampleAsync()
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{
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// Before the gRPC native library (gRPC Core) is lazily loaded and initialized,
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// an environment variable must be set so BoringSSL is configured to use ECDSA TLS
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// certificates (required by lbcwallet).
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Environment.SetEnvironmentVariable("GRPC_SSL_CIPHER_SUITES", "HIGH+ECDSA");
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var walletAppData = Portability.LocalAppData(Environment.OSVersion.Platform, "lbcwallet");
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var walletTlsCertFile = Path.Combine(walletAppData, "rpc.cert");
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var cert = await FileUtils.ReadFileAsync(walletTlsCertFile);
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var channel = new Channel("localhost:19244", new SslCredentials(cert));
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try
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{
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var c = WalletService.NewClient(channel);
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var balanceRequest = new BalanceRequest
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{
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AccountNumber = 0,
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RequiredConfirmations = 1,
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};
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var balanceResponse = await c.BalanceAsync(balanceRequest);
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Console.WriteLine($"Spendable balance: {balanceResponse.Spendable} Satoshis");
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}
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finally
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{
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await channel.ShutdownAsync();
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}
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}
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}
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static class FileUtils
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{
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public static async Task<string> ReadFileAsync(string filePath)
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{
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using (var r = new StreamReader(filePath, Encoding.UTF8))
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{
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return await r.ReadToEndAsync();
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}
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}
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}
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static class Portability
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{
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public static string LocalAppData(PlatformID platform, string processName)
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{
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if (processName == null)
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throw new ArgumentNullException(nameof(processName));
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if (processName.Length == 0)
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throw new ArgumentException(nameof(processName) + " may not have zero length");
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switch (platform)
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{
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case PlatformID.Win32NT:
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return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
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ToUpper(processName));
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case PlatformID.MacOSX:
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return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal),
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"Library", "Application Support", ToUpper(processName));
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case PlatformID.Unix:
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return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal),
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ToDotLower(processName));
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default:
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throw new PlatformNotSupportedException($"PlatformID={platform}");
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}
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}
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private static string ToUpper(string value)
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{
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var firstChar = value[0];
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if (char.IsUpper(firstChar))
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return value;
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else
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return char.ToUpper(firstChar) + value.Substring(1);
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}
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private static string ToDotLower(string value)
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{
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var firstChar = value[0];
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return "." + char.ToLower(firstChar) + value.Substring(1);
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}
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}
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}
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```
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## Node.js
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First, install gRPC (either by building the latest source release, or
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by installing a gRPC binary development package through your operating
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system's package manager). This is required to install the npm module
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as it wraps the native C library (gRPC Core) with C++ bindings.
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Installing the [grpc module](https://www.npmjs.com/package/grpc) to
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your project can then be done by executing:
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```
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npm install grpc
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```
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A Node.js client does not require generating JavaScript stub files for
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the wallet's API from the `.proto`. Instead, a call to `grpc.load`
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with the `.proto` file path dynamically loads the Protobuf descriptor
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and generates bindings for each service. Either copy the `.proto` to
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the client project directory, or reference the file from the
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`lbcwallet` project directory.
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```JavaScript
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// Before the gRPC native library (gRPC Core) is lazily loaded and
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// initialized, an environment variable must be set so BoringSSL is
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// configured to use ECDSA TLS certificates (required by lbcwallet).
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process.env['GRPC_SSL_CIPHER_SUITES'] = 'HIGH+ECDSA';
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var fs = require('fs');
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var path = require('path');
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var os = require('os');
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var grpc = require('grpc');
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var protoDescriptor = grpc.load('./api.proto');
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var walletrpc = protoDescriptor.walletrpc;
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var certPath = path.join(process.env.HOME, '.lbcwallet', 'rpc.cert');
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if (os.platform == 'win32') {
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certPath = path.join(process.env.LOCALAPPDATA, 'lbcwallet', 'rpc.cert');
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} else if (os.platform == 'darwin') {
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certPath = path.join(process.env.HOME, 'Library', 'Application Support',
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'lbcwallet', 'rpc.cert');
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}
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var cert = fs.readFileSync(certPath);
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var creds = grpc.credentials.createSsl(cert);
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var client = new walletrpc.WalletService('localhost:19244', creds);
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var request = {
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account_number: 0,
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required_confirmations: 1
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};
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client.balance(request, function(err, response) {
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if (err) {
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console.error(err);
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} else {
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console.log('Spendable balance:', response.spendable, 'Satoshis');
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}
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});
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```
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## Python
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**Note:** gRPC requires Python 2.7.
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After installing gRPC Core and Python development headers, `pip`
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should be used to install the `grpc` module and its dependencies.
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Full instructions for this procedure can be found
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[here](https://github.com/grpc/grpc/blob/master/src/python/README.md).
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Generate Python stubs from the `.proto`:
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```bash
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$ protoc -I /path/to/lbryio/lbcwallet/rpc --python_out=. --grpc_out=. \
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--plugin=protoc-gen-grpc=$(which grpc_python_plugin) \
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/path/to/lbcwallet/rpc/api.proto
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```
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Implement the client:
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```Python
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import os
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import platform
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from grpc.beta import implementations
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import api_pb2 as walletrpc
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timeout = 1 # seconds
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def main():
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# Before the gRPC native library (gRPC Core) is lazily loaded and
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# initialized, an environment variable must be set so BoringSSL is
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# configured to use ECDSA TLS certificates (required by lbcwallet).
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os.environ['GRPC_SSL_CIPHER_SUITES'] = 'HIGH+ECDSA'
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cert_file_path = os.path.join(os.environ['HOME'], '.lbcwallet', 'rpc.cert')
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if platform.system() == 'Windows':
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cert_file_path = os.path.join(os.environ['LOCALAPPDATA'], "lbcwallet", "rpc.cert")
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elif platform.system() == 'Darwin':
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cert_file_path = os.path.join(os.environ['HOME'], 'Library', 'Application Support',
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'lbcwallet', 'rpc.cert')
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with open(cert_file_path, 'r') as f:
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cert = f.read()
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creds = implementations.ssl_client_credentials(cert, None, None)
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channel = implementations.secure_channel('localhost', 19244, creds)
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stub = walletrpc.beta_create_WalletService_stub(channel)
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request = walletrpc.BalanceRequest(account_number = 0, required_confirmations = 1)
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response = stub.Balance(request, timeout)
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print 'Spendable balance: %d Satoshis' % response.spendable
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if __name__ == '__main__':
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main()
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```
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