Why I'm not being able to connect several simulators to my ocpp server

Question

I'm creating an OCPP server, using the node-ts-ocpp library.
This is the code:

import{ OcppServer, OcppClientConnection, BootNotificationRequest, BootNotificationResponse } from '@extrawest/node-ts-ocpp'

const simpleCentralSystem = new OcppServer()
simpleCentralSystem.listen(9220)

console.log("Corriendo en 9220 :)")

simpleCentralSystem.on('connection', (client: OcppClientConnection) =>{
    console.log(`Cliente ${client.getCpId()} conectado`)
    client.on('close', (code: number, reason: Buffer) =>{
        console.log(`El cliente ${client.getCpId()} se desconectó`, code, reason.toString())
    })
    client.on('BootNotification', (request: BootNotificationRequest, cb: (response: BootNotificationResponse) => void) => {
        const response: BootNotificationResponse = {
            status: 'Accepted',
            currentTime: new Date().toISOString(),
            interval: 60,
        };
        cb(response);
    });
})

Now my problem is that I can only connect to this server the simulator that comes in the examples of the library, but cannot connect a physical charger or this simulator.