Respond to signal ping / pong (#871)

* Respond to signal ping / pong

* Pass back 1 for pong for now, we don't need the timestamp

* update protocol

pkg/rtc/participant_signal.go

@@ -54,6 +54,9 @@ func (p *ParticipantImpl) SendJoinResponse(
 				// indicates both server and client support subscriber as primary
 				SubscriberPrimary:   p.SubscriberAsPrimary(),
 				ClientConfiguration: p.params.ClientConf,
+				// sane defaults for ping interval & timeout
+				PingInterval: 10,
+				PingTimeout:  20,
 			},
 		},
 	})

pkg/service/rtcservice.go

@@ -256,6 +256,14 @@ func (s *RTCService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 		}
+		if _, ok := req.Message.(*livekit.SignalRequest_Ping); ok {
+			_ = sigConn.WriteResponse(&livekit.SignalResponse{
+				Message: &livekit.SignalResponse_Pong{
+					Pong: 1,
+				},
+			})
+			continue
+		}
 		if err := reqSink.WriteMessage(req); err != nil {
 			pLogger.Warnw("error writing to request sink", err,
 				"connID", connId)