0x00 C00PacketLoginStart
Starts the login process by sending the player's GameProfile (username) to the server.
Fields
| Field | Type | Description |
|---|---|---|
| profile | GameProfile | Player's GameProfile containing the username (UUID is null at this stage) |
Wire Encoding
| Field | Type | Notes |
|---|---|---|
| Username | String (max 16) | The player's Minecraft username |
MCP References
MCP
NetHandlerLoginServer.processLoginStart()Handler Interface
HND
INetHandlerLoginServerNotes
Sent immediately after C00Handshake (with state=LOGIN). The GameProfile has a username but the UUID is null — the server fills in the UUID from Mojang's auth servers and returns it in S02PacketLoginSuccess. This is the first step of the login handshake after the initial HANDSHAKING state.
implementation Implementation Cases
NameSpoof
(Gugustus)
Intercept login start to spoof username before authentication.
if (event.getPacket() instanceof C00PacketLoginStart) {
((C00PacketLoginStart) event.getPacket()).gameProfile.name = "SpoofedName";
}CrackedBypass
(Gugustus)
Intercept login start to spoof username before authentication.
if (event.getPacket() instanceof C00PacketLoginStart) {
((C00PacketLoginStart) event.getPacket()).gameProfile.name = "SpoofedName";
}