Custom External Bus Messaging Gateway Recommendations

[SteveBush]

I want to write a custom external bus and messaging gateway that sends secure, encrypted messages between one or more network agents hosted by my application on a home network. I'm building a mobile/desktop application that discovers and manages devices and services on a home network. The messages are used to find out the properties and capabilities of services hosted on a remote agent. The messaging payload is encrypted JSON and requires authorization to decrypt and execute commands.

For example, I want to discover all of the music playlists and music players on a home network, process and consolidate the results, and redistribute the results to all agents. The user could then invoke an authorized command: Play "Katherine's Favorites" music playlist from Katherine's device (IOS, Android, MacOS, Windows Desktop) on the Sonos in the Family Room. Events signal device command and status updates: song being played, volume level changed, mute, etc. I use Brighter as a common messaging framework over Bonjour, UPnP, and other discovery, eventing, and command protocols.

I use SQLite as my Inbox and Outbox database provider, as it's available on all target platforms I support. My plan is to write a messaging gateway that does the following:

1. Use the routing key to determine whether the message should be routed internally or sent to an external agent. The routing key starts with local or the GUID of the network agent to which the message should be routed.
2. For outbound internal messages, decide if the message should be placed in the Inbox or routed on the internal bus.
3. For outbound external messages, map the agent ID to an IPAddress:Port for the hosted agent. Encrypt and send the message to the remote agent via TCP/IP, who deposits it in the Outbox.
4. The agent monitors the Inbox, decrypts and validates the message payload, and processes messages using the internal bus. The local agent message handler generates the appropriate replies or events and deposits them in the Outbox for distribution either locally or remotely.

I'm looking for advice on implementation and the best place to start.

Thanks

[SteveBush]

Rather than write a custom gateway, I have decided to use MQTTnet to host a broker on a remote agent. It's lightweight, open source, handles TLS, automatic topic generation, and meets most of my requirements. My plan is to contribute to the MQTT gateway in Brighter as that will benefit the community.