I am developing an online tabletop program, eventually be used for Dungeons and Dragons most likely. While I am skilled enough in the aspects of the program operating on its own, I am entirely new to the idea of networking programs to one another through the internet. I plan to have a dynamic board that all users of the program can view and edit, which will update in real time, as well as a chat box where dice rolls and chat messages can be posted for all users to see, again updating in real time.
If someone could give me advice as to reading material that I can use to teach myself how to do this, I would be really grateful. I am asking mostly because I am unsure where exactly to start, as well as what areas of networking I will need to learn in order to accomplish the goals and abilities of the program.
Hopefully the material will be online, be it on a webpage or easily accessible pdf. I do have a few books on java, but hope not to purchase more unless absolutely necessary.
Again, this is just to help me focus on what I need to learn in order to accomplish the project. Of course I realize I could google "java networking" and get some tips, but I am looking for a resource that someone has (hopefully) used in the past and recommends it to a moderately skilled java user like myself for their first foray into learning networking.