Party System

Hello, I am looking for guidance on the best approach to creating a party system I already have the backbone and a system working with commands but I am looking to attach this to a ui(just finished making) so I am looking for advice on the best way to do this going forward, I assume packets will play a big part in the communication to so I can get access to EntityPlayerMP as I believe for the client its EntityClientPlayerMP, So I have a couple of functions that handle it all : 

createParty(EntityPlayerMP player);

joinParty(EntityPlayerMP player, int inviteIdentifier);

inviteParty(EntityPlayerMP sender, EntityPlayerMP invitedPlayer);

Will I need to create different packets and messages for each of these ? if so my idea for the inviteParty is to send over the invitedPlayer uuid but how do I then receive the the player from the current Minecraft server?

Any information will be appreciated.

Regards,

Discult