Doing this can be very buggy, I recommend not doing it on a hosted server, since it requires all the users to have the add-on.
exec("Add-ons/*/Server.cs");transmitDatablocks();
Replace the * with the name of the add-ons, minus the .zip.
This goes inside the console, which you can bring up with the ` key, located below ESC, and to the left of 1/!.
The reason the other users have to have the add-ons is because they need the datablocks/files, and it will kick them out if someone equips the item.
Now, if its simply a script or something, its fine to use it inside a hosted server.