You have already answered your question in your own words:
Quote:
there would be a server which has an instance and receives messages from all the textboxes to what is being edited. This way I can also send messages from the server regarding the position of the cursors in the other applications and even inject text if required and resolve any conflicts.
You need to code this out. WPF provides the Keyboard control at only one cursor, so you would need to abstract the direct control of the keyboard and mouse events too. See this thread for more on this,
Collaborative WPF Application - Multiple Keyboards and Mice - Stack Overflow[
^], but it is not impossible. Just a lot hard and tough to do that.
If I had to do this, I would start with a single user editing the document and a central server handling the edit-events and performing those actions on a central document. Then, from there, increase the user count one by one up to 5-10. A normal document editor provides support for a limited number of users because you need to lock the document or provide concurrent access. As already mentioned in Solution 1, this would require a complete article/project to explain how it would work in WPF, a QA is not a fit for this. Try searching for an article in the top-right corner.
Check this too,
Collaborative editing - Wikipedia[
^]