WebRTC - Failed to set sdp remote response: Called in wrong state: STATE_INPROGRESS

I am following the example here: https://www.w3.org/TR/webrtc/#simple-peer-to-peer-example

I changed the code because I only need one-way transmission:

var configuration = null; //{ "iceServers": [{ "urls": "stuns:stun.example.org" }] };
var peerConnection;

var outboundPeerStream = null;
var outboundPeerStreamSessionId = null;

var createPeerConnection = function () {
    if (peerConnection)
        return;

    peerConnection = new RTCPeerConnection(configuration);

    // send any ice candidates to the other peer
    peerConnection.onicecandidate = function (event) {
        signalrModule.sendClientNotification(JSON.stringify({ "candidate": event.candidate }));
    };

    // let the "negotiationneeded" event trigger offer generation
    peerConnection.onnegotiationneeded = peerStreamingModule.sendOfferToPeers;

    // once remote track arrives, show it in the remote video element
    peerConnection.ontrack = function (event) {
        var inboundPeerStream = event.streams[0];
        remoteStreamHelper.pushStreamToDom(inboundPeerStream, foo);
    }
}

// this gets called either on negotiationNeeded and every 30s to ensure all peers have the offer from the stream originator
peerStreamingModule.sendOfferToPeers = function () {
    peerConnection.createOffer().then(function (offer) {
        return peerConnection.setLocalDescription(offer);
    }).then(function () {
        // send the offer to the other peer
        signalrModule.sendClientNotification(JSON.stringify({ "desc": peerConnection.localDescription}));
    }).catch(logger.internalLog);
};

// this gets called by the stream originator when the stream is available to initiate streaming to peers
peerStreamingModule.initializeWithStream = function (outboundStream, sessionId) {
    outboundPeerStream = outboundStream;
    outboundPeerStreamSessionId = sessionId;
    createPeerConnection();
    peerConnection.addStream(outboundStream);
    //peerStreamingModule.sendOfferToPeers(); I don't think I need this...
}

peerStreamingModule.handleP2PEvent = function (notification) {
    if (!peerConnection)
        createPeerConnection();

    if (notification.desc) {
        var desc = notification.desc;
        // if we get an offer, we need to reply with an answer
        if (desc.type == "offer") {
            peerConnection.setRemoteDescription(desc).then(function () {
                return peerConnection.createAnswer();
            }).then(function (answer) {
                return peerConnection.setLocalDescription(answer);
            }).then(function () {
               signalrModule.sendClientNotification(JSON.stringify({ "desc": peerConnection.localDescription, "sessionId": sessionManager.thisSession().deviceSessionId() }), app.username());
            }).catch(logger.internalLog);
        } else if (desc.type == "answer") {

  peerConnection.setRemoteDescription(desc).catch(logger.internalLog);
        } else {
            logger.internalLog("Unsupported SDP type. Your code may differ here.");
        }
    } else
        pc.addIceCandidate(notification.candidate).catch(logger.internalLog);
}

      

        
        
        
      

    

This seems to work, but I am puzzled by two parts:

1) WebRTC - Failed to set remote answer sdp: Called in wrong state: STATE_INPROGRESS

- this appears from time to time in my logs - am I doing something wrong in the above, what is causing this?

2) Am I doing sendOfferToPeers

and correctly initializeWithStream

? I'm afraid firing sendOfferToPeers

on an interval from the creator isn't how the spec is supposed to be; my goal is to ensure that all peers end up receiving an offer no matter when they join or if they encounter connectivity issues that discard the original offer / negotiation.