问WebRTC无法添加ICE候选人

EN

function processSignalingMessage(message) {
        var msg = JSON.parse(message);

        if (msg.type === 'offer') {
            // Callee creates PeerConnection
            if (!initiator && !started)
                maybeStart();

            // We only know JSEP version after createPeerConnection().
            if (isRTCPeerConnection)
                pc.setRemoteDescription(new RTCSessionDescription(msg));
            else
                pc.setRemoteDescription(pc.SDP_OFFER,
                        new SessionDescription(msg.sdp));

            doAnswer();
        } else if (msg.type === 'answer' && started) {
            pc.setRemoteDescription(new RTCSessionDescription(msg));
        } else if (msg.type === 'candidate' && started) {
            var candidate = new RTCIceCandidate({
                sdpMLineIndex : msg.label,
                candidate : msg.candidate
            });
            pc.addIceCandidate(candidate);
        } else if (msg.type === 'bye' && started) {
            onRemoteHangup();
        }
    }