Development resources

Map File Format
See these pages for information on Map Editing:

Map Editing (general)

Map Editing (hex)

Java Classes to Deserialize Maps

Packet Protocol
(Disclaimer: This information is guaranteed up to v0.30/1.10.1, protocol v7)

Token Meanings:

Note: The first byte of every packet identifies its type. For example in packet 0x06, the first c is 0x06. In 0x03, the first c is 0x03. Etc, etc. A number following a token indicates multiple of them. For example c4 is equivalent to cccc.

Resources
(Disclaimer: This information is currently strongly biased towards the C programming language)