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package hotline
import (
"bytes"
"encoding/binary"
"errors"
"io"
)
type handshake struct {
Protocol [4]byte // Must be 0x54525450 TRTP
SubProtocol [4]byte
Version [2]byte // Always 1
SubVersion [2]byte
}
var trtp = [4]byte{0x54, 0x52, 0x54, 0x50}
// Handshake
// After establishing TCP connection, both client and server start the handshake process
// in order to confirm that each of them comply with requirements of the other.
// The information provided in this initial data exchange identifies protocols,
// and their versions, used in the communication. In the case where, after inspection,
// the capabilities of one of the subjects do not comply with the requirements of the other,
// the connection is dropped.
//
// The following information is sent to the server:
// Description Size Data Note
// Protocol ID 4 TRTP 0x54525450
// Sub-protocol ID 4 HOTL User defined
// VERSION 2 1 Currently 1
// Sub-version 2 2 User defined
//
// The server replies with the following:
// Description Size Data Note
// Protocol ID 4 TRTP
// Error code 4 Error code returned by the server (0 = no error)
func Handshake(rw io.ReadWriter) error {
handshakeBuf := make([]byte, 12)
if _, err := io.ReadFull(rw, handshakeBuf); err != nil {
return err
}
var h handshake
r := bytes.NewReader(handshakeBuf)
if err := binary.Read(r, binary.BigEndian, &h); err != nil {
return err
}
if h.Protocol != trtp {
return errors.New("invalid handshake")
}
_, err := rw.Write([]byte{84, 82, 84, 80, 0, 0, 0, 0})
return err
}
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