Start the server and let it generate a new protocol_key.txt
Stop the server
Delete the protocol_key.txt file
wget https://gist.githubusercontent.com/Bluscream/5531ceefd86fcf7efc0c5519072fb2d6/raw/5e86b287a9f72bb047f9717d0f78bd11acee867e/protocol_key.txt
Then start the server again