client: fix reading sources without server ports (bluenviron/mediamtx#4253) (#796)

RTCP packets were sent out to nil addresses, due to the lack of server
ports, causing an error.

client_format.go

@@ -67,7 +67,7 @@ func (cf *clientFormat) start() {
 			Period:    cf.cm.c.receiverReportPeriod,
 			TimeNow:   cf.cm.c.timeNow,
 			WritePacketRTCP: func(pkt rtcp.Packet) {
-				if cf.cm.udpRTPListener != nil {
+				if cf.cm.udpRTPListener != nil && cf.cm.udpRTCPListener.writeAddr != nil {
 					cf.cm.c.WritePacketRTCP(cf.cm.media, pkt) //nolint:errcheck
 				}
 			},

client_play_test.go

@@ -843,6 +843,10 @@ func TestClientPlayAnyPort(t *testing.T) {
 
 			serverDone := make(chan struct{})
 			defer func() { <-serverDone }()
+
+			serverTerminate := make(chan struct{})
+			defer close(serverTerminate)
+
 			go func() {
 				defer close(serverDone)
 
@@ -960,14 +964,20 @@ func TestClientPlayAnyPort(t *testing.T) {
 					require.Equal(t, &testRTCPPacket, packets[0])
 					close(serverRecv)
 				}
+
+				<-serverTerminate
 			}()
 
 			packetRecv := make(chan struct{})
 
 			c := Client{
 				AnyPortEnable:        true,
+				receiverReportPeriod: 100 * time.Millisecond,
 			}
 
+			clientErr := make(chan struct{})
+			defer func() { <-clientErr }()
+
 			var med *description.Media
 			err = readAll(&c, "rtsp://localhost:8554/teststream",
 				func(medi *description.Media, _ format.Format, pkt *rtp.Packet) {
@@ -978,6 +988,12 @@ func TestClientPlayAnyPort(t *testing.T) {
 			require.NoError(t, err)
 			defer c.Close()
 
+			go func() {
+				err := c.Wait()
+				require.EqualError(t, err, "terminated")
+				close(clientErr)
+			}()
+
 			<-packetRecv
 
 			if ca == "random" {
@@ -985,6 +1001,13 @@ func TestClientPlayAnyPort(t *testing.T) {
 				require.NoError(t, err)
 				<-serverRecv
 			}
+
+			// make sure that RTCP receiver reports do not cause any error
+			select {
+			case <-time.After(200 * time.Millisecond):
+			case <-clientErr:
+				t.Error("should not happen")
+			}
 		})
 	}
 }