In general that's the procedure to follow for a new game :
- Check if somebody already did something even partially, if so read their code, take what you can, learn the general structure of things
- If nothing exists, boot up Wireshark, look if the protocol is encrypted, textual, binary, you might have some luck at this point
- If Wireshark failed, download the vanilla game binaries, identify what language it was, if java based (or c#) decompile, try to find the packet classes. If native you can try using idapro but it's going to be harder
- Assuming some of the above worked, document the protocol
- Implement the low level (tcp, udp, encryption, compression, splitting)
- Implement parsing and serialisation (we use protodef for this)
- Implement login sequence At this point you have something on the level of node-minecraft-protocol