javascript - Uncaught (in promise) DOMException: Cannot set remote answer in state stable

one text

i have #client.js file

const socket=io("/");
var userid=Math.floor(Math.random()*100000);
socket.emit("user-joined",userid);

var localvideo,remotevideo,remotestream,localstream;
localvideo=document.getElementById("local");
remotevideo=document.getElementById("remote");
async function init(){
    const server={"iceserver":[{"urls":['stun:stun1.1.google.com','stun:stun2.1.google.com']}]}
    const peerconnection=new RTCPeerConnection(server)
    localstream=await navigator.mediaDevices.getUserMedia({video:true,audio:false});
    localvideo.srcObject=localstream;
    localstream.getTracks().forEach((track)=>{
    peerconnection.addTrack((track),localstream);
    })
    remotestream=new MediaStream();
    
    peerconnection.ontrack=e=>{
        e.streams[0].getTracks().forEach((track)=>{
            remotestream.addTrack((track));
            remotevideo.srcObject=remotestream;
        })
    }
    
    peerconnection.onicecandidate=(e)=>{
        if(e.candidate){
        send({
            type:"candidate",
            candidate:e.candidate,
            name:userid
        });

        console.log(e.candidate)
    }
    }
   let offer=await peerconnection.createOffer()
   await peerconnection.setLocalDescription(offer)
    send({
        type:"offer",
        offer:offer,
        name:userid
    });



    socket.on("message",async(message)=>{
    
        var data={};
        try {
            data=JSON.parse(message)
           
        } catch (error) {
            console.log("invalid json")
            data={};
        }
        switch(data.type){
            case "candidate":
                if(userid!=data.sender){
                    peerconnection.addIceCandidate(new RTCIceCandidate(data.candidate))
                }           
               break;
       
           case "offer":
               if(userid!=data.name){
                peerconnection.setRemoteDescription(new RTCSessionDescription(data.offer));
                let answer=await peerconnection.createAnswer()
                await peerconnection.setLocalDescription(answer);
                send({
                   type:"answer",
                   answer:answer,
                   name:data.sender 
                })
               }
               break;
           
           case "answer":
            if(userid===data.sender){
                peerconnection.setRemoteDescription(new RTCSessionDescription(data.answer))
            }
               
          }
    })

}
init()
function send(message){
    socket.emit("message",JSON.stringify(message));
}

server.js code am trying to make the code work in the way that if only one user has joined the room,no offer or candidate flows and on second user joining offers and candidates flow.i have tried this repeatedly but i cant see my remote video coming up. i don`t know what to do help bros and sis. am just a newbie so much in need of knowing #webrtc

const express=require('express');
const app=express();
const server=require('http').createServer(app);
const io=require('socket.io')(server);
const {v4:uuidv4}=require('node-uuid');
var users=[];
app.set('view engine','ejs');
app.use(express.static('public'));
app.get('/',(req,res)=>{
    res.redirect('/'+uuidv4());
})
app.get('/:room',(req,res)=>{
    res.render('room',{roomId:req.params.room})
})

io.on("connection",connection=>{

    connection.on("user-joined",userid=>{
        console.log("user: "+userid+" joined room");
        users.push(userid)
        console.log("users:",users)

        if(users.length>1){
        connection.on("message",message=>{
         var data={};
         try {
            data=JSON.parse(message)
         } catch (error) {
            console.log("invalid json",error);
            data={};
         }
         switch(data.type){
            case "candidate":
                for(let i=0;i<users.length;i++){
                    if(data.name!=users[i]){
                        send({
                            type:"candidate",
                            candidate:data.candidate,
                            sender:data.name
                        })
                        console.log("candidates sent")
                    }
                    
                }
                break;
            case "offer": 
            for(let i=0;i<users.length;i++){
                if(data.name!=users[i]){
                    send({
                        type:"offer",
                        offer:data.offer,
                        sender:data.name
                    })
                    console.log("offer sent")
                }
                
            }
            break; 
            
           case "answer":
            send({
                type:"answer",
                answer:data.answer,
                sender:data.name
            })
              break; 
         }


        })

        }
    })
    

    }) 
function send(message){
    io.emit("message",JSON.stringify(message));
}








server.listen(3000,()=>{
    console.log("server listening at port 3000")
});