MySQL 9.5.0
Source Code Documentation
Protocol::HandshakeV9:

Initial handshake packet for protocol version 9.

Payload
TypeNameDescription
int<1> protocol version Always 9
string<NUL> server version human readable status information
int<4> thread id a.k.a. connection id
string<NUL> scramble Authentication plugin data for Old Password Authentication
Returns
Protocol::HandshakeResponse320