Consider a product where changes a client is making to a text file are broadcast to other clients via a Server. The broadcast happens when the person making changes in the editor presses a button. Other client are connected using a tcpip pipe so no polling is required
In our current solution each time the button is pressed the entire Text is sent and broadcast and receivers just drop the old text and replace with the new
Charmingly simple as this approach is, when the size of this text goes up and the number of users dramatically increases and ,any many such groups of users talk to the same server for their needs, then badness ensues

So we want to transmit deltas. However on the receiving side its more like merging deltas.( its an HTML editor so even stuff like font changes , colors etc lists all have to be transmitted, and of course people have an annoying habit of deleting stuff as well ) My questions are

1) are there well known algorithms in the literature that solve this issue ( and reasonably implementable by mortals )
2) Are there shrinkwrapped products I can buylicenseopensource that basically solve this diff and merge problem