95 lines
2.3 KiB
Go
95 lines
2.3 KiB
Go
package signaller
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import (
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"encoding/json"
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"fmt"
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"log"
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"net/http"
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"time"
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"github.com/gorilla/websocket"
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"github.com/pion/webrtc/v4"
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)
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// WebSocketSignaller exchanges SDP through WebSocket connections.
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// Stealthier than HTTP polling — single persistent connection,
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// looks like a normal web app or live data feed (Technique 3).
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type WebSocketSignaller struct {
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baseURL string
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sessionKey string
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role string
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}
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// NewWebSocketSignaller creates a WebSocket-based signaller client.
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func NewWebSocketSignaller(baseURL, sessionKey, role string) *WebSocketSignaller {
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return &WebSocketSignaller{
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baseURL: baseURL,
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sessionKey: sessionKey,
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role: role,
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}
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}
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// SendLocalDescription sends this peer's SDP via WebSocket.
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func (w *WebSocketSignaller) SendLocalDescription(sdp webrtc.SessionDescription) error {
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url := fmt.Sprintf("%s?sess=%s&role=%s&action=sdp", w.baseURL, w.sessionKey, w.role)
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dialer := websocket.Dialer{
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HandshakeTimeout: 10 * time.Second,
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}
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conn, _, err := dialer.Dial(url, http.Header{})
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if err != nil {
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return fmt.Errorf("ws-signaller: dial: %w", err)
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}
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defer conn.Close()
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data, err := json.Marshal(sdp)
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if err != nil {
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return fmt.Errorf("ws-signaller: marshal: %w", err)
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}
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if err := conn.WriteMessage(websocket.TextMessage, data); err != nil {
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return fmt.Errorf("ws-signaller: write: %w", err)
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}
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return nil
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}
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// ReceiveRemoteDescription waits for and returns the remote peer's SDP.
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func (w *WebSocketSignaller) ReceiveRemoteDescription() (*webrtc.SessionDescription, error) {
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url := fmt.Sprintf("%s?sess=%s&role=%s&action=wait", w.baseURL, w.sessionKey, w.role)
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dialer := websocket.Dialer{
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HandshakeTimeout: 10 * time.Second,
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}
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conn, _, err := dialer.Dial(url, http.Header{})
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if err != nil {
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return nil, fmt.Errorf("ws-signaller: dial: %w", err)
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}
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defer conn.Close()
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for {
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_, msg, err := conn.ReadMessage()
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if err != nil {
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return nil, fmt.Errorf("ws-signaller: read: %w", err)
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}
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// Check for error response
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var errResp struct {
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Error string `json:"error"`
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}
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if json.Unmarshal(msg, &errResp) == nil && errResp.Error != "" {
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return nil, fmt.Errorf("ws-signaller: %s", errResp.Error)
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}
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var sdp webrtc.SessionDescription
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if err := json.Unmarshal(msg, &sdp); err != nil {
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log.Printf("[ws-signaller] bad sdp: %v", err)
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continue
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}
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return &sdp, nil
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}
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}
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