Tim (beatle) has posted a new multiplayer.dll in the community downloads section to replace the existing one. You can download it from here:
This is a multiplayer fix to allow direct IP connections in Prepar3D 1.1. To use this fix, simply replace your multiplayer.dll with the one available for download here. The multiplayer.dll that should be replaced can be found in your installation directory (typically C:\Program Files\Lockheed Martin\Prepar3D).
The fix will be rolled into the next release of Prepar3D.