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|
package m4p
import (
"context"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"log"
"net"
"time"
)
// Client represents an active connection to the magic4pc server.
type Client struct {
ctx context.Context
cancel context.CancelFunc
conn net.Conn
opts dialOptions
serverKeepalive chan struct{}
recvBuf chan Message
}
type dialOptions struct {
updateFrequency int
filters []string
}
// DialOption sets options for dial.
type DialOption func(*dialOptions)
// WithUpdateFrequency sets the RemoteUpdate frequency.
func WithUpdateFrequency(f int) func(*dialOptions) {
return func(o *dialOptions) {
o.updateFrequency = f
}
}
// WithFilters specifies the filters used for RemoteUpdate.
func WithFilters(filters ...string) func(*dialOptions) {
return func(o *dialOptions) {
o.filters = filters
}
}
// Dial connects to a magic4pc server running in webOS.
func Dial(ctx context.Context, addr string, opts ...DialOption) (*Client, error) {
o := dialOptions{
updateFrequency: 250,
filters: DefaultFilters,
}
for _, opt := range opts {
opt(&o)
}
d := &net.Dialer{
Timeout: 5 * time.Second,
}
conn, err := d.DialContext(ctx, "udp4", addr)
if err != nil {
return nil, err
}
ctx, cancel := context.WithCancel(context.Background())
c := &Client{
ctx: ctx,
cancel: cancel,
conn: conn,
opts: o,
serverKeepalive: make(chan struct{}, 1),
recvBuf: make(chan Message, 10), // Buffer up to 10 messages after which we block.
}
// Register our client with the server.
m := NewMessage(SubSensorMessage)
m.Register = &Register{
UpdateFrequency: c.opts.updateFrequency,
Filter: c.opts.filters,
}
err = c.Send(m)
if err != nil {
c.Close()
return nil, fmt.Errorf("register failed: %w", err)
}
// Tell the server that we're alive and well.
go c.keepalive()
go c.recv()
return c, nil
}
func (c *Client) recv() {
var buf [1024]byte
recvLoop:
for {
select {
case <-c.ctx.Done():
return
default:
}
n, err := c.conn.Read(buf[:])
if err != nil {
if errors.Is(err, net.ErrClosed) {
log.Printf("m4p: Client: recv: connection closed: %v", err)
return
}
log.Printf("m4p: Client: recv: read udp packet failed: %v", err)
continue
}
m, err := decode(buf[:n])
if err != nil {
log.Printf("m4p: Client: recv: decode failed: %v", err)
continue
}
switch m.Type {
case KeepAliveMessage:
// log.Printf("m4p: Client: recv: got %s", m.Type)
// Trigger server keepalive, non-blocking (chan is buffered).
select {
case c.serverKeepalive <- struct{}{}:
default:
}
goto recvLoop
case InputMessage:
log.Printf("m4p: Client: recv: got %s: %v", m.Type, m.Input)
case RemoteUpdateMessage:
log.Printf("m4p: Client: recv: got %s: %s", m.Type, hex.EncodeToString(m.RemoteUpdate.Payload))
default:
log.Printf("m4p: Client: recv: unknown message: %s", m.Type)
}
select {
case c.recvBuf <- m:
default:
log.Printf("m4p: Client: recv: buffer full, discarding message: %s", m.Type)
}
}
}
func (c *Client) keepalive() {
defer c.Close()
serverDeadline := time.After(keepaliveTimeout)
clientKeepalive := time.After(clientKeepaliveInterval)
for {
select {
case <-c.ctx.Done():
return
case <-c.serverKeepalive:
serverDeadline = time.After(keepaliveTimeout)
case <-serverDeadline:
log.Printf("m4p: Client: keepalive: server keepalive deadline reached, disconnecting...")
return
case <-clientKeepalive:
_, err := c.conn.Write([]byte("{}"))
if err != nil {
if errors.Is(err, net.ErrClosed) {
log.Printf("m4p: Client: keepalive: connection closed: %v", err)
return
}
log.Printf("m4p: Client: keepalive: send client keepalive failed, disconnecting...")
return
}
clientKeepalive = time.After(clientKeepaliveInterval)
}
}
}
// Send a message to the magic4pc server.
func (c *Client) Send(m Message) error {
b, err := json.Marshal(m)
if err != nil {
return fmt.Errorf("json encode message failed: %w", err)
}
if _, err = c.conn.Write(b); err != nil {
return fmt.Errorf("write message failed: %w", err)
}
return nil
}
// Recv messages from the magic4pc server. Keepalives are handled
// transparently by the client and are not observable.
func (c *Client) Recv(ctx context.Context) (Message, error) {
select {
case <-ctx.Done():
return Message{}, ctx.Err()
case <-c.ctx.Done():
return Message{}, c.ctx.Err()
case m := <-c.recvBuf:
return m, nil
}
}
// Close the client and connection.
func (c *Client) Close() error {
c.cancel()
return c.conn.Close()
}
|
