Why does Socket.io catch just one connection without client side

So if we implement socket into node server, and add a code (event handler) to follow a connection, it will show the first connection but not the others.
I understand it is working normally if we implement in the html a socket client side but i don’t understand why it is just showing just first connection that has been cought if we dont implement a socket client side.

const express = require("express")
const { readFileSync } = require("fs")
let http = require("http")
const {Server} = require("socket.io")


let app = express()

let server = http.createServer(app)

let socket = new Server(server)



app.get("/", (request, response)=> {
    response.send(`<center>
        <h1>CEKANJE NA DOVOLJAN BROJ KORISNIKA
        </h1>
        </center>`)
})


socket.on("connection", (korisnik)=>{
    console.log(korisnik.id) 
})


server.listen(5000, ()=> {
    console.log("server pokrenut")
})