This mod allows to check the mods present on the client, when it connects to a server. The server has a file called modpack-mods-list.json which contains the mods that must be present on the client (You have to manually configure this either by putting the mods you want the client to have when it connects). When the client connects to the server, the client sends the names of the .jar files for each mods present in the mods folder. The server then checks if the mods sent match the list. If it does, the player will not be disconnected.
IMPORTANT: the fileHash has to use the SHA-256 algorithm
check this video to understand how it works -> https://youtu.be/HDsvAae6k78