This is what the author of the FSHost program wrote in the Prepare3d Multiplayers forum:
Hi guys, I'm the author of FSHostClient.
Just a quick note to confirm that yes, it does work with P3D. There were some problems with the way other aircraft were displayed though, so I've just now released version 1.2 of FSHostClient with full support for Prepar3D. Check it out and let me know if you find any issues.