Transport agnostic interfaces

First of all this is really a great and useful framework.

I would like to raise the question or rather a discussion weather the interfaces are transport agnostic yes or no. If i am right in my conclusion they are not. Why?

The http client client.hpp and iclientconnector.hpp are implemented in a synchronous request/response pattern, therefore offering a Send method with return type std::string
A tcp client is preferably implemented in asynchronous send/receive pattern, therefore client.hpp and iclientconnector.hpp cannot be used 'agnostically' out of the box
For using json-rpc-cxx with a tcp client/server, the iclientconnector.hpp and client.hpp have to be extended by offering, e.g. a Post method without a return value and a MessageHandler, e.g.

iclientconnector.hpp

using MessageHandler = std::function<void(const std::string)>;
virtual void Post(const std::string &request) = 0;
MessageHandler OnMessage;

client.hpp

using MessageHandler = std::function<void(const JsonRpcResponse)>;
JsonRpcClient(IClientConnector &connector, version v) : connector(connector), v(v)
{
    connector.OnMessage = [this](const std::string &message)
    {
        json response = json::parse(message);
        JsonRpcResponse rpc_response{};
        ...
        OnMessage(rpc_response);
    }
}
...
MessageHandler OnMessage;

client.cpp

std::future<JsonRpcResponse> future;
std::promise<JsonRpcResponse> promise;
JsonRpcResponse response;
client.OnMessage = [&] (const JsonRpcResponse &response) mutable
{
    promise.set_value(response);
};
future = promise.get_future();
client.CallMethod(1, "GetProduct", {"0xff"});
response = future.get();
std::cout << response.result.dump() << std::endl;

jsonrpcx / json-rpc-cxx

Transport agnostic interfaces #34