使用SipJs 0.17.1和freeswitch 1.10.5。Debian 10。眩晕:stun.l.google.com: 19302<param name="apply-candidate-acl" value="wan.auto"/>
如果用户使用任何家庭或办公室互联网，当接到电话时，音频在0.2秒内出现。
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.103910 [NOTICE] switch_rtp.c:4952 Activating RTP audio ICE: UpI7:gafAlEO8WSw1T9B3 109.201.xxx.xxx:9646
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.103910 [INFO] switch_core_media.c:8896 Skipping RTCP ICE (Same as RTP)
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.103910 [INFO] switch_rtp.c:3764 Activate RTP/RTCP audio DTLS client
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.103910 [INFO] switch_rtp.c:3927 Changing audio DTLS state from OFF to HANDSHAKE
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.243916 [INFO] switch_rtp.c:3282 Changing audio DTLS state from HANDSHAKE to SETUP
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.263910 [INFO] switch_rtp.c:3189 audio Fingerprint Verified.
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.263910 [INFO] switch_rtp.c:4254 Activating audio Secure RTP SEND
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.263910 [INFO] switch_rtp.c:4232 Activating audio Secure RTP RECV
9bd6fc2d-fe49-4a05-8a43-b400e4ce3565 2021-01-16 21:39:29.263910 [INFO] switch_rtp.c:3231 Changing audio DTLS state from SETUP to READY
但是当用户使用移动互联网和接电话时，音频出现在1.5秒左右(主观上更长)。
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:40.003922 [NOTICE] switch_rtp.c:4952 Activating RTP audio ICE: rzCc:NJN0su78A6fbnv6q 89.42.xxx.xxx:45466
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:40.003922 [INFO] switch_core_media.c:8896 Skipping RTCP ICE (Same as RTP)
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:40.003922 [INFO] switch_rtp.c:3764 Activate RTP/RTCP audio DTLS client
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:40.003922 [INFO] switch_rtp.c:3927 Changing audio DTLS state from OFF to HANDSHAKE
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.243907 [NOTICE] switch_rtp.c:1301 Auto Changing audio stun/rtp/dtls port from 89.42.xxx.xxx:45466 to 89.42.xxx.xxx:63930 idx:1
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.403925 [INFO] switch_rtp.c:3282 Changing audio DTLS state from HANDSHAKE to SETUP
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.423918 [INFO] switch_rtp.c:3189 audio Fingerprint Verified.
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.423918 [INFO] switch_rtp.c:4254 Activating audio Secure RTP SEND
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.423918 [INFO] switch_rtp.c:4232 Activating audio Secure RTP RECV
7518c5c2-a045-4535-9630-97a20c4cd980 2021-01-16 23:37:41.423918 [INFO] switch_rtp.c:3231 Changing audio DTLS state from SETUP to READY
为什么行出现Auto Changing audio stun/rtp/dtls?是什么导致了端口的变化?如何避免耗时的端口切换?
在WebRTC中建立连接使用一种称为ICE (https://www.rfc-editor.org/rfc/rfc8445)的协议。ICE首先尝试在对等体之间建立直接连接，只有在此失败后才返回使用TURN中继。
在您的示例中，很可能从您的办公网络成功进行直接连接，但是移动客户端需要使用TURN服务器，这只会在超时后发生。如果您知道需要一个TURN服务器，您可以通过在建立对端连接时指定{iceTransportPolicy: 'relay'}来避免超时。