How to listen to Server-sent Events on SAPUI5 - https

Question

I'm trying to make my SAPUI5 app deployed on Sap Cloud Platform listen to server-sent events sent from a simple test server.
I found this tutorial: https://auth0.com/blog/developing-real-time-web-applications-with-server-sent-events/
The tutorial explains how to create a React app that displays a table with some information and how to use server-sent events to make the server update the information on the client without the client having to make periodic requests to the server.
I tested it and got it working, and now I'm trying to substitute the React client app for my SAPUI5 app.
I added a HANA destination in my sap account and added the destination in my neo-app file.
This is basically the controller for the app:
onInit: function () {
this.eventSource = new EventSource('/flightinfo/events');
this.eventSource.addEventListener('flightStateUpdate', this.updateFlightState, false);
}
updateFlightState: function(event) {
console.log("Hello");
}
And this is how the destination is declared in the neo-app.json file:
{
"path": "/flightinfo",
"target": {
"type": "destination",
"name": "flightinfo"
},
"description": "flightinfo"
}
I expected my app to print to the console every time the server sent an update, since I'm just testing the connection and not using the data received. However, the app doesn't fire the event that would trigger the console output.
My server log shows the request is received and the response is 200 OK, but the webapp shows the response as timed out:
HTTP Status 504 - Socket connection timed out for host [my server]. Reason: Read timed out (local port [port number] to address [ip address] ([...].od.sap.biz), remote port [port number] to address [ip address] ([...].od.sap.biz))
I redacted IPs and Ports from the error message.
Trying to open the request url from the network tab at chrome responds with:
HTTP Status 503 - No application is available to handle this request
However, navigating manually to the address of my server (the address I introduced in the Destinations tab on SCP) does show me the data that my server is sending, updates and all.
What am I getting wrong? Is there some security policy preventing my server from sending server-sent events through a SCP Destination?
Any help would be greatly appreciated, since I can't seem to find any information about using server-sent events on SAPUI5 anywhere.
Thank you!