All messages begin with 0x01, followed by the content length length. The content length length is the length of the content length and representated by one byte. Then follows the content length and after that the message content.

Handshake

Server: Server protocol, version
Encryption
1. Client: Serialized client public key
2. Server: Serialized server public key
3. Client: Client nonce
4. Server: Server nonce
5. Client: Random bytes (encrypted)
6. Server: received bytes from client (not encrypted)
The client closes the connection if the received bytes from server (7.) do not match the generated bytes (6.) to prevent malfunction and test the encryption.
Server authentication
1. Server: Server certificate
The client closes the connection if it does not trust the server certificate.
Client authentication
1. Client: Client certificate
The server closes the connection if the client is unauthorized.