Minimal Login

The bare minimum number of packets to join a Server with a Notchian Client is as follows.

Packet	Contents
C->S Handshake	Giving the server the client name
S->C Handshake	Gives the client a connection hash
C->S Login	Gives the server info about the client
S->C Login	Gives the client info about the to-be-used player and world
S->C Player Position and Look	Sets the players position in the world

A vanilla client will become responsive upon receiving the player’s initial starting position and rotation from the server. After this, the client will continuously send Position and Look packets as needed.

This will place the player into an empty world at sunrise. The player will begin to fall shortly after connecting, since there are no solid blocks for it to collide with.

Vanilla Login

Packet	Contents
C->S Handshake	Giving the server the client name
S->C Handshake	Gives the client a connection hash
C->S Login	Gives the server info about the client
S->C Login	Gives the client info about the to-be-used player and world
S->C Spawn Point	Sets the players spawn
S->C Time	Sets the current time
S->C Health	Sets the shown health
S->C Window Items	Sets the players inventory

This is followed by a bunch of Pre-Chunk packets to load the chunks, and Chunk packets which contain the actual chunk data, alongside the Server and Client exchanging position and rotation information.