index.js

const express = require("express")
const app = express()
var http = require('http').createServer(app);
var io = require('socket.io')(http);
app.use(express.static("./public"))

let model = [];
let X = "X";
let O = "O";
let BLANK = " ";
let BOARD_FULL = "BOARD FULL";


for (let i = 0; i < 9; i++) {
    model[i] = BLANK;
}

app.get("/getModel", (req, res) => {
    console.log("Someone got the model")
    let toSend = JSON.stringify(model);
    console.log(toSend);
    res.send(toSend);
})

app.get("/setModel/:model", (req,res)=>{
    model = req.params.model;
    console.log(model);
    res.send("ok");

})

io.on('connection', function(socket){
    console.log('a user connected ' + socket.id);
    
    socket.on('getModel', function(msg){
      console.log("getModel")
      socket.emit('model', JSON.stringify(model));
      
    });

    socket.on("setModel", function(msg){
      console.log("set model", msg);
      model = JSON.parse(msg);
      socket.broadcast.emit("model", JSON.stringify(model));
    })
    
    socket.on('disconnect', function(){
      console.log("disconnected");
    })
  });

http.listen(5555, function (err) {
// app.listen(5555, function (err) {
    if (err) return console.error(err);
    console.log("We are listening on http://localhost:5555");
})