rpc.hpp

A simple header-only library for supporting remote procedure calls using a variety of extensible features.

License

rpc.hpp is licensed under the BSD 3-Clause License.

Features

• Cross-platform.
  • Supports every major compiler/operating system.
• Easy to use.
  • Only requires a few lines of code to provide the implementation of your client or server.
• Modern.
  • Takes advantage of a lot of compile-time and generic programming features such as C++17's constexpr if.
• Fast.
  • See COMPARISON to see how this library compares to the likes of librpc and gRPC.
• Support for various types.
  • std::string / std::vector supported out of the box (more STL containers to come).
  • Users can create serialization member functions for their own custom types.
    • Users can also provide template methods for serializing types outside of their control
• Extensible support via "adapters".
  • Currently supported:
    • nlohmann-json
    • rapidjson
    • Boost.JSON
    • bitsery

Known Limitations

• Pointers and arrays (other than const char* / const char[] for strings) cannot be passed across an RPC boundary.
• Functions with default arguments should not be used with remote procedure calls as the default argument(s) must be provided each time anyway.
• Function overloads will not work across an RPC boundary as the server will have an ambiguous call.
  • This includes non-explicit template functions (see examples for the syntax for calling template functions remotely).
• Not (statically) type-safe across the RPC boundary.
  • This is the nature of a dynamic system like remote procedure calls.
  • Return type and explicit parameters must be specified at call site.
  • Exceptions will be able to catch function signature mismatches.
  • Function signatures can be provided via a shared header to allow for strict compile-time type-checking (by using call_header_func()).

Documentation

See Doxygen docs here.

Basic Example

For more examples see examples.

server.cpp

#define RPC_HPP_SERVER_IMPL

#include <rpc_adapters/rpc_njson.hpp>

#include <string>

using rpc_hpp::adapters::njson;
using rpc_hpp::adapters::njson_adapter;

int Add(int n1, int n2)
{
    return n1 + n2;
}

void AppendStr(std::string& str, const char* append)
{
    str.append(append);
}

class RpcServer : public rpc_hpp::server_interface<njson_adapter>
{
public:
    RpcServer(const char* address)
    {
        // initialize server...
    }

    // ...

    void Run()
    {
        std::string data;

        // Get data from client...

        // Sink data into the dispatch function to get result data
		auto result_data = dispatch(std::move(data));

        // Send result data back to client...
    }
};

int main()
{
    RpcServer my_server{"address"};
    my_server.bind("Add", &Add);
    my_server.bind("AppendStr",
        [](std::string& str, const std::string& append) {
            AppendStr(str, append.c_str());
        }
    );

    while (true)
    {
        my_server.Run();
    }
}

client.cpp

#define RPC_HPP_CLIENT_IMPL

#include <rpc_adapters/rpc_njson.hpp>

#include <cassert>
#include <string>

using rpc_hpp::adapters::njson_adapter;

class RpcClient : public rpc_hpp::client_interface<njson_adapter>
{
public:
    RpcClient(const char* address)
    {
        // initialize client...
    }

    // ...

private:
    void send(const std::string& mesg) override
    {
        // Send mesg to server...
    }

    void send(std::string&& mesg) override
    {
        // Send mesg to server...
    }

    std::string receive() override
    {
        // Get message back from server...
    }
};

int main()
{
    RpcClient my_client{ "address" };

    const auto result = my_client.template call_func<int>("Sum", 1, 2);
    assert(result == 3);

    std::string str{ "Hello" };
    my_client.call_func("AppendStr", str, " world!");
    assert(str == "Hello world!");
}