MSGHUB

This is a lightweight asynchronous message bus C++ library based on Boost.Asio. It allows to connect, send and receive custom messages to virtually any number of local or network clients.

The idea is simple... there are topics, subscribers and publishers.

One client create a msghub instance and others are connecting to it.

Subscriber specify the topic name of its interest. All clients publish message into a topic and hub distribute messages across all subscribers.

Message is a byte array or a string.

Array may contain any serialized user data, but it's out of scope here.

Examples

1. Create hub, subscribe on "any topic" and publish "new message" into "any topic":

   namespace mh = msghublib;
   
   // Message handler
   void on_message(std::string_view topic, mh::span<char const> message)
   {
       // handle message
   }
   
   int main()
   {
       boost::asio::io_context io;
       // Create hub to listen on 0xbee port
       mh::msghub hub(io.get_executor());
       hub.create(0xbee);
   
       // Subscribe on "any topic"
       hub.subscribe("any topic", on_message);
   
       // Current or any another client
       hub.publish("any topic", "new message");
   
       io.run(); // keep server active, if created
   }

2. Connect to hub on "localhost" and publish "new message" into "any topic":

   namespace mh = msghublib;
   
   int main()
   {
       boost::asio::io_context io;
       mh::msghub hub(io.get_executor());
       hub.connect("localhost", 0xbee);
       hub.publish("any topic", "new message");
   
       hub.stop();
       io.run();
   }

3. Using multiple threads

   namespace mh = msghublib;
   
   int main()
   {
       boost::asio::thread_pool io(5); // count optional
       mh::msghub hub(io.get_executor());
       hub.connect("localhost", 0xbee);
       hub.publish("any topic", "new message");
   
       hub.stop();
       io.join();
   }

Note: span<char const> is std::span<char const> on c++20 capable compilers.