MqttRPC

MqttRPC is a RPC library for C++ and uses MQTT as its underlying transport.

While there are many rpc libraries available, they are all typically based on a traditional client-server implemention. This forces one-to-one relationships between entities ultimately leading to scalabiltiy issues for larger distributed systems with both one-to-one and one-to-many relationships between entities.

MqttRPC tries to introduce a concept of a peer and unlike tradtional client-sever relationship it is bidrectional and supports one-to-many and many-to-many rpc.

MqttRPC doesn't use any IDL and is extremely lightweight. And most importantly, unlike its peers, it doesn't use boost and is threading model agnostic. It is straight forward to embed this in an existing event loop.

MqttRPC is cross platform and been tested with VS 2017 and gcc 6.3.

Example

Setup a mqtt broker e.g mosquitto or emqtt

#include <iostream>
#include "Rpc.h"

void main()
{
    auto& mqtt_instance = mqtt::MQTT::Instance();
    // connect to mqtt with a unique client id. 
    mqtt_instance.Connect("TestID", "127.0.0.1", 1883);

    bool shut_down = false; 

    // peer connection objects define one side of a connection and can exist on different mqtt clients. 
    rpc::PeerConnection peer_one, peer_two; 

    // if a connection can be defined as A-B
    // one side of the connection will be initialized as 
    peer_one.Init("A", "B");
    // and other as 
    peer_two.Init("B", "A"); 
    // peer_one & peer_two are now connected. 
    // and rpc on each other.

    peer_one.Bind("message", [&](int number) {
        std::cout << "message: number: " << number << std::endl;
        shut_down = true;
    });

    peer_two.Bind("update", [&](const std::string& message,const int number) {
        std::cout << "update:  message: " << message << " number: " << number << std::endl;
    });

    peer_one.Call("update", " Hello ! ", 10);
    peer_two.Call("message",  10);

    while (!shut_down)
    {
        // call this in your event tick, whatever thread. 
        mqtt_instance.Loop();
    }
}

A slighlty more detailed example.

MqttRPC uses two really awesome projects.

• cereal A C++11 library for serialization
• mosquitto Eclipse Foundation.

Current Uses

• In a cross platform production system with almost 700 entities rpc'ng each other, passing around 500k messages a day.

Build

git clone --recursive git@github.com:ankitkk/MqttRPC.git
mkdir build 
cd build 
cmake ..\MqttRPC 
cd ..\MqttRPC ; make SimpleExample; 
./SimpleExample