webrtc is working on all browsers but not working on firefox

before anything ! i have checked all answers in similar questions and the answers wasn't usefull and old . i have tried to use webrtc on firefox but it did not work ! and no error was givin !

this code work on all browsers but firefox

this is my code

let configuration = {

        "iceServers":[{
            'url':'stun:stun.l.google.com:19302'
        }]

};


io.on("signaling_message",(data)=>{

    //displayMessage(data.message);
    if(!rtcPeerConn){
       startSignaling();
     }

     if(data.type!="user_here"){
         let message  = JSON.parse(data.message);
         if(message.sdp){
             rtcPeerConn.setRemoteDescription(new RTCSessionDescription(message.sdp),()=>{
                 if(rtcPeerConn.remoteDescription.type=="offer"){
                     rtcPeerConn.createAnswer(sendLocalDesc,logerror)
                 }
             })
         }else{

            rtcPeerConn.addIceCandidate(new RTCIceCandidate(message.candidate));
         }
     }

})

function startSignaling(){
    displayMessage("start signaling...");
  rtcPeerConn = new RTCPeerConnection(configuration);
 //send ice candidate to other peer
        rtcPeerConn.onicecandidate  = function(evt){
            if(evt.candidate){
                io.emit("signal",{"type":"ice candidate","message":JSON.stringify({'candidate':evt.candidate}),room:signal_room})
                displayMessage("completed that ice candidate");
            }
        }
rtcPeerConn.onnegotiationneeded = function(){
    displayMessage("on negotiationnneded");
    rtcPeerConn.createOffer(sendLocalDesc,logerror);

}
rtcPeerConn.onaddstream = (evt,err)=>{
    displayMessage("creating  the other stream");
    if(err){
        displayMessage(err)
    }
    success2(evt.stream);
}

navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia;

        navigator.mediaDevices.getUserMedia({video:true,audio:true}).then(stream=>{
             success(stream);
             rtcPeerConn.addStream(stream);
        }).catch(err=>{
             logerror(err);
            });

}


function sendLocalDesc(desc){

rtcPeerConn.setLocalDescription(desc,()=>{
displayMessage("set local description");
io.emit("signal",{type:"SDP",message:JSON.stringify({'sdp':rtcPeerConn.localDescription}),room:signal_room})


},logerror);

}


     function success(stream){
        if ("srcObject" in video) {
        video.srcObject = stream;
        } else {
        // Avoid using this in new browsers, as it is going away.
        video.src = window.URL.createObjectURL(stream);
        }

        video.play();
        }




        function success2(stream){
        if ("srcObject" in video2) {
        video2.srcObject = stream;
        } else {
        // Avoid using this in new browsers, as it is going away.
        video2.src = window.URL.createObjectURL(stream);
        }


        video2.play();
        }

is there anything wrong with my code?

another question , can i use google stun iceservers on production ? are they reliable?

EDIT

the firefox stuck at this script

  rtcPeerConn.onicecandidate  = function(evt){
            if(evt.candidate){
                io.emit("signal",{"type":"ice candidate","message":JSON.stringify({'candidate':evt.candidate}),room:signal_room})
                displayMessage("completed that ice candidate");
            }
        }

it keeps displaying this message (completed that ice candidate) like a loop