I am trying to create a mod that will only become active when the client connects to my test server.

 

this means that when the client trys to play on single player or on any other server, I want the mod to act like it isn't really there.

I also want to add a debug mode, which will allow it to connect to anything when debug active.

 

But I am not sure what would be the best way to achieve this, and i am seeking some help.

That's hard to say. the mod/mods could range from adding guis to blocks and entities, as well as changing how things work.

Thanks.

I will try this and play around a bit, and see what i can do.