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connect.go
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connect.go
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package packets
import (
"bytes"
"encoding/binary"
"fmt"
"io"
)
// Connect represents the MQTT Connect packet
type Connect struct {
FixHeader *FixHeader
//Variable header
ProtocolLevel byte
//Connect Flags
UsernameFlag bool
ProtocolName []byte
PasswordFlag bool
WillRetain bool
WillQos uint8
WillFlag bool
WillTopic []byte
WillMsg []byte
CleanSession bool
KeepAlive uint16 //如果非零,1.5倍时间没收到则断开连接[MQTT-3.1.2-24]
//if set
ClientID []byte
Username []byte
Password []byte
AckCode uint8 //ack的返回码
}
// String is mainly used in logging, debugging and testing.
func (c *Connect) String() string {
return fmt.Sprintf("Connect, ProtocolLevel: %v, UsernameFlag: %v, PasswordFlag: %v, ProtocolName: %s, CleanSession: %v, KeepAlive: %v, ClientID: %s, Username: %s, Password: %s"+
", WillFlag: %v, WillRetain: %v, WillQos: %v, WillMsg: %s",
c.ProtocolLevel, c.UsernameFlag, c.PasswordFlag, c.ProtocolName, c.CleanSession, c.KeepAlive, c.ClientID, c.Username, c.Password, c.WillFlag, c.WillRetain, c.WillQos, c.WillMsg)
}
// Pack encodes the packet struct into bytes and writes it into io.Writer.
func (c *Connect) Pack(w io.Writer) error {
var err error
c.FixHeader = &FixHeader{PacketType: CONNECT, Flags: FLAG_RESERVED}
remainLength := 10 + len(c.ClientID) + 2
if c.WillFlag {
remainLength += len(c.WillTopic) + 2 + len(c.WillMsg) + 2
}
if c.UsernameFlag {
remainLength += len(c.Username) + 2
}
if c.PasswordFlag {
remainLength += len(c.Password) + 2
}
c.FixHeader.RemainLength = remainLength
err = c.FixHeader.Pack(w)
if err != nil {
return err
}
lenProtocolName := []byte{0, 4}
w.Write(lenProtocolName)
w.Write(c.ProtocolName)
w.Write([]byte{c.ProtocolLevel})
var (
usenameFlag = 0
passwordFlag = 0
willRetain = 0
willFlag = 0
willQos = 0
cleanSession = 0
reserved = 0
)
if c.UsernameFlag {
usenameFlag = 128
}
if c.PasswordFlag {
passwordFlag = 64
}
if c.WillRetain {
willRetain = 32
}
if c.WillQos == 1 {
willQos = 8
} else if c.WillQos == 2 {
willQos = 16
}
if c.WillFlag {
willFlag = 4
}
if c.CleanSession {
cleanSession = 2
}
connFlag := usenameFlag | passwordFlag | willRetain | willFlag | willQos | cleanSession | reserved
w.Write([]byte{uint8(connFlag)})
keepAlive := make([]byte, 2)
binary.BigEndian.PutUint16(keepAlive, c.KeepAlive)
w.Write(keepAlive)
clienIDByte, _, erro := EncodeUTF8String(c.ClientID)
if erro != nil {
return erro
}
_, err = w.Write(clienIDByte)
if c.WillFlag {
willTopicByte, _, _ := EncodeUTF8String(c.WillTopic)
w.Write(willTopicByte)
willMsgByte, _, erro := EncodeUTF8String(c.WillMsg)
_, err = w.Write(willMsgByte)
if erro != nil {
return erro
}
}
if c.UsernameFlag {
usernameByte, _, erro := EncodeUTF8String(c.Username)
_, err = w.Write(usernameByte)
if erro != nil {
return erro
}
}
if c.PasswordFlag {
passwordByte, _, erro := EncodeUTF8String(c.Password)
_, err = w.Write(passwordByte)
if erro != nil {
return erro
}
}
return err
}
// Unpack read the packet bytes from io.Reader and decodes it into the packet struct.
func (c *Connect) Unpack(r io.Reader) error {
restBuffer := make([]byte, c.FixHeader.RemainLength)
_, err := io.ReadFull(r, restBuffer)
if err != nil {
return err
}
if !bytes.Equal(restBuffer[0:6], []byte{0, 4, 77, 81, 84, 84}) { //protocol name
return ErrInvalProtocolName // [MQTT-3.1.2-1] 不符合的protocol name直接关闭
}
c.ProtocolName = []byte{77, 81, 84, 84}
c.ProtocolLevel = restBuffer[6]
if c.ProtocolLevel != 0x04 {
c.AckCode = CodeUnacceptableProtocolVersion // [MQTT-3.1.2-2]
}
connectFlags := restBuffer[7]
reserved := 1 & connectFlags
if reserved != 0 { //[MQTT-3.1.2-3]
return ErrInvalConnFlags
}
c.CleanSession = (1 & (connectFlags >> 1)) > 0
c.WillFlag = (1 & (connectFlags >> 2)) > 0
c.WillQos = 3 & (connectFlags >> 3)
if !c.WillFlag && c.WillQos != 0 { //[MQTT-3.1.2-11]
return ErrInvalWillQos
}
c.WillRetain = (1 & (connectFlags >> 5)) > 0
if !c.WillFlag && c.WillRetain { //[MQTT-3.1.2-11]
return ErrInvalWillRetain
}
c.PasswordFlag = (1 & (connectFlags >> 6)) > 0
c.UsernameFlag = (1 & (connectFlags >> 7)) > 0
c.KeepAlive = binary.BigEndian.Uint16(restBuffer[8:10])
return c.unpackPayload(restBuffer[10:])
}
func (c *Connect) unpackPayload(restBuffer []byte) error {
var vh []byte
var size int
var err error
vh, size, err = DecodeUTF8String(restBuffer)
if err != nil {
return err
}
restBuffer = restBuffer[size:]
c.ClientID = vh
if len(c.ClientID) == 0 && c.CleanSession == false { //[MQTT-3.1.3-7]
c.AckCode = CodeIdentifierRejected //[MQTT-3.1.3-8]
}
if c.WillFlag {
vh, size, err = DecodeUTF8String(restBuffer)
if err != nil {
return err
}
restBuffer = restBuffer[size:]
c.WillTopic = vh
vh, size, err = DecodeUTF8String(restBuffer)
if err != nil {
return err
}
restBuffer = restBuffer[size:]
c.WillMsg = vh
}
if c.UsernameFlag {
vh, size, err = DecodeUTF8String(restBuffer)
if err != nil {
return err
}
restBuffer = restBuffer[size:]
c.Username = vh
}
if c.PasswordFlag {
vh, size, err = DecodeUTF8String(restBuffer)
if err != nil {
return err
}
restBuffer = restBuffer[size:]
c.Password = vh
}
return nil
}
// NewConnectPacket returns a Connect instance by the given FixHeader and io.Reader
func NewConnectPacket(fh *FixHeader, r io.Reader) (*Connect, error) {
//b1 := buffer[0] //一定是16
p := &Connect{FixHeader: fh}
//判断 标志位 flags 是否合法[MQTT-2.2.2-2]
if fh.Flags != FLAG_RESERVED {
return nil, ErrInvalFlags
}
err := p.Unpack(r)
if err != nil {
return nil, err
}
return p, err
}
// NewConnackPacket returns the Connack struct which is the ack packet of the Connect packet.
func (c *Connect) NewConnackPacket(sessionReuse bool) *Connack {
//b1 := buffer[0] //一定是16
ack := &Connack{}
ack.Code = c.AckCode
if c.CleanSession == true { //[MQTT-3.2.2-1]
ack.SessionPresent = 0
} else {
if sessionReuse {
ack.SessionPresent = 1 //[MQTT-3.2.2-2]
} else {
ack.SessionPresent = 0 //[MQTT-3.2.2-3]
}
}
if ack.Code != CodeAccepted {
ack.SessionPresent = 0
}
return ack
}