install go2rtc on bob

installs_on_host/go2rtc/pkg/mqtt/client.go

@@ -0,0 +1,112 @@
+package mqtt
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"net"
+	"time"
+)
+
+const Timeout = time.Second * 5
+
+type Client struct {
+	conn net.Conn
+	mid  uint16
+}
+
+func NewClient(conn net.Conn) *Client {
+	return &Client{conn: conn, mid: 2}
+}
+
+func (c *Client) Connect(clientID, username, password string) (err error) {
+	if err = c.conn.SetDeadline(time.Now().Add(Timeout)); err != nil {
+		return
+	}
+
+	msg := NewConnect(clientID, username, password)
+	if _, err = c.conn.Write(msg.b); err != nil {
+		return
+	}
+
+	b := make([]byte, 4)
+	if _, err = io.ReadFull(c.conn, b); err != nil {
+		return
+	}
+
+	if !bytes.Equal(b, []byte{CONNACK, 2, 0, 0}) {
+		return errors.New("wrong login")
+	}
+
+	return
+}
+
+func (c *Client) Subscribe(topic string) (err error) {
+	if err = c.conn.SetDeadline(time.Now().Add(Timeout)); err != nil {
+		return
+	}
+
+	c.mid++
+	msg := NewSubscribe(c.mid, topic, 1)
+	_, err = c.conn.Write(msg.b)
+	return
+}
+
+func (c *Client) Publish(topic string, payload []byte) (err error) {
+	if err = c.conn.SetDeadline(time.Now().Add(Timeout)); err != nil {
+		return
+	}
+
+	c.mid++
+	msg := NewPublishQOS1(c.mid, topic, payload)
+	_, err = c.conn.Write(msg.b)
+	return
+}
+
+func (c *Client) Read() (string, []byte, error) {
+	if err := c.conn.SetDeadline(time.Now().Add(Timeout)); err != nil {
+		return "", nil, err
+	}
+
+	b := make([]byte, 1)
+	if _, err := io.ReadFull(c.conn, b); err != nil {
+		return "", nil, err
+	}
+
+	size, err := ReadLen(c.conn)
+	if err != nil {
+		return "", nil, err
+	}
+
+	b0 := b[0]
+	b = make([]byte, size)
+	if _, err = io.ReadFull(c.conn, b); err != nil {
+		return "", nil, err
+	}
+
+	if b0&0xF0 != PUBLISH {
+		return "", nil, nil
+	}
+
+	i := binary.BigEndian.Uint16(b)
+	if uint32(i) > size {
+		return "", nil, errors.New("wrong topic size")
+	}
+
+	b = b[2:]
+
+	if qos := (b0 >> 1) & 0b11; qos == 0 {
+		return string(b[:i]), b[i:], nil
+	}
+
+	// response with packet ID
+	_, _ = c.conn.Write([]byte{PUBACK, 2, b[i], b[i+1]})
+
+	return string(b[2:i]), b[i+2:], nil
+}
+
+func (c *Client) Close() error {
+	// TODO: Teardown
+	return c.conn.Close()
+}

installs_on_host/go2rtc/pkg/mqtt/message.go

@@ -0,0 +1,122 @@
+package mqtt
+
+import (
+	"io"
+)
+
+type Message struct {
+	b []byte
+}
+
+// https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html
+const (
+	CONNECT   = 0x10
+	CONNACK   = 0x20
+	PUBLISH   = 0x30
+	PUBACK    = 0x40
+	SUBSCRIBE = 0x82
+	SUBACK    = 0x90
+	QOS1      = 0x02
+)
+
+func (m *Message) WriteByte(b byte) {
+	m.b = append(m.b, b)
+}
+
+func (m *Message) WriteBytes(b []byte) {
+	m.b = append(m.b, b...)
+}
+
+func (m *Message) WriteUint16(i uint16) {
+	m.b = append(m.b, byte(i>>8), byte(i))
+}
+
+func (m *Message) WriteLen(i int) {
+	for i > 0 {
+		b := byte(i % 128)
+		if i /= 128; i > 0 {
+			b |= 0x80
+		}
+		m.WriteByte(b)
+	}
+}
+
+func (m *Message) WriteString(s string) {
+	m.WriteUint16(uint16(len(s)))
+	m.b = append(m.b, s...)
+}
+
+func (m *Message) Bytes() []byte {
+	return m.b
+}
+
+const (
+	flagCleanStart = 0x02
+	flagUsername   = 0x80
+	flagPassword   = 0x40
+)
+
+func NewConnect(clientID, username, password string) *Message {
+	m := &Message{}
+	m.WriteByte(CONNECT)
+	m.WriteLen(16 + len(clientID) + len(username) + len(password))
+
+	m.WriteString("MQTT")
+	m.WriteByte(4) // MQTT version
+	m.WriteByte(flagCleanStart | flagUsername | flagPassword)
+	m.WriteUint16(30) // keepalive
+
+	m.WriteString(clientID)
+	m.WriteString(username)
+	m.WriteString(password)
+	return m
+}
+
+func NewSubscribe(mid uint16, topic string, qos byte) *Message {
+	m := &Message{}
+	m.WriteByte(SUBSCRIBE)
+	m.WriteLen(5 + len(topic))
+
+	m.WriteUint16(mid)
+	m.WriteString(topic)
+	m.WriteByte(qos)
+	return m
+}
+
+func NewPublish(topic string, payload []byte) *Message {
+	m := &Message{}
+	m.WriteByte(PUBLISH)
+	m.WriteLen(2 + len(topic) + len(payload))
+
+	m.WriteString(topic)
+	m.WriteBytes(payload)
+	return m
+}
+
+func NewPublishQOS1(mid uint16, topic string, payload []byte) *Message {
+	m := &Message{}
+	m.WriteByte(PUBLISH | QOS1)
+	m.WriteLen(4 + len(topic) + len(payload))
+
+	m.WriteString(topic)
+	m.WriteUint16(mid)
+	m.WriteBytes(payload)
+	return m
+}
+
+func ReadLen(r io.Reader) (uint32, error) {
+	var i uint32
+	var shift byte
+
+	b := []byte{0x80}
+	for b[0]&0x80 != 0 {
+		if _, err := r.Read(b); err != nil {
+			return 0, err
+		}
+
+		i += uint32(b[0]&0x7F) << shift
+		shift += 7
+	}
+
+	return i, nil
+}