WebRTC doesn't work

Test WebRTC with https://apprtc.appspot.com, cannot estimate the connection whenever it's session holder or joining the session.

For session holder, he will get following error when connecting to the joiner:
States:
Signaling: stable
Gathering: complete
Connection: connected
Local: HOST:16 TURN:2
Remote: HOST:8 STUN:8 TURN:8
LocalAddr: 10.57.85.91:61002
RemoteAddr: 10.184.186.125:49697

Stats:
Setup time: 9506ms

Failed to set session description: Failed to set remote answer sdp: Session error code: ERROR_CONNECT. Session error description: Failed to add send stream ssrc: 530543098.

For the joiner, he will get similar error when connecting to the holder:
Connecting...
States:
Signaling: stable
Gathering: complete
Connection: new
Local: HOST:32 TURN:4
Remote: HOST:4 STUN:4 TURN:4

Stats:
Setup time: NaNms
Failed to set session description: Failed to set remote answer sdp: Session error code: ERROR_CONNECT. Session error description: Failed to set audio send codecs..