Connected Doors

Connected Doors makes double doors open and close together when right-clicking or redstone powering either of the sides.
It's recommended, but not required to install the mod both server and client side.

When installed only on the server:
Everything will work, but clients without the mod won't see double doors open in perfect sync.

When installed only on the client:
You can open double doors by hand. This is done by telling the server you right-clicked both doors, so it might not work on servers with anti-cheat mods / plugins.

New in version 1.2:
Fence gates are now connected. The mod also has a config now where you can turn this feature off or tweak the range.
In addition, you can turn the client side features off for specific servers by adding the server name or address to the respective blacklist. Entries are separated by semicolons ( ; ).