index.js

const app = require("express")();
const server = require("http").createServer(app);
const cors = require("cors");
const { Socket } = require("socket.io");
const io = require("socket.io")(server,{
    cors:{
        origin : "*",
        methods : ["GET", "POST"]
    }
});

app.use(cors());

const PORT = process.env.PORT || 5000;
 app.get("/",(req,res) => {
     res.send("Server is running.")
     
 });
 io.on('connection', (socket) => {
     socket.emit('me', socket.id);
     socket.on('disconnect', () => {
         socket.broadcast.emit("callended");

     });
     socket.on('calluser', ({ userTocall , signalData , from , name }) => {
         io.to(userToCall).emit("calluser", { signal : signalData, from , name});

     });
     socket.io("answercall" , (data) => {
         io.to(data.to).emit("callaccepted", data.signal);
     })
    });

 server.listen(PORT, () => console.log('Server listening on port ${PORT}'));