Why does the server return ERR_Packet in response to COM_INIT_DB?

Question

MySQL

After a successful authorization phase, the client generates a COM_INIT_DB packet. It's built right! When trying to send it to the server, the server returns an Unknown Command error (But this is at the TCP level).
Php script writes the following error:
Error while reading INIT_DB's OK packet. PID=8828
It's correct, I just write an intermediate link between the client and the server, and I redirect and receive packets myself...
Please tell me what's wrong...
PS:
The data packet that I send to the server: 07 00 00 00 02 64 69 70 6C 6F 6D Example COM_INIT_DB: dev.mysql.com/doc/internals/en/com-init-db.html
In response, the server returns an ERR Packet, but why?