I needed to start working on the Tag Event Notification feature in OpenDAX. This is a pretty important feature that would allow a module to sit and wait for things to happen in the server instead of having to poll the server for information like it does now.
I decided that writing slave functionality into the modbus module would be a good way to test this. Then I decided that would be too easy so I decided to add Modbus TCP Server (Slave) functionality. It's eventually going to have to be done. The slave/server functionality in the module would simply wait for updates to happen in the tags that represent the data tables before sending the data to the library data areas that represent the different modbus registers.
I really need to get the modbus module to as close to 100% as I can get it. This system needs to be useful for something or nobody will ever use it, and it won't get any development beyond what I am able to put into it. If the modbus module were complete, the Lua module complete and the base system (server / library) were in good shape then it'd make a pretty good little modbus RTU. So I decided to work on the slave/server functionality as a way to use the new event notification feature.