websocket connection between services in kubernetes - kubernetes

Question

I have two services in Kubernetes (k3s) one is backend and another is frontend and I need the transfer data from backend to fronted through websocket. When I debug in docker-compose it works. So when run in docker-compose on backend I have (python):
import websockets
...
start_server = websockets.serve(server, "0.0.0.0", 8001)
...
On front I have (html):
...
var ws = new WebSocket('ws://localhost:8001');
...
And I have function onclose:
ws.onclose = function (e) {
document.getElementById("textArea").innerHTML = 'Socket is closed. Reconnect will be attempted in 5 seconds...' + e.reason;
setTimeout(function () {
connect();
}, 5000);
};
And it's works as should.
When I use k3s I get Socket is closed. Reconnect will be attempted in 5 seconds...
There is my backend (app) deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: app-deployment
namespace: my-namespace
labels:
app: app
spec:
replicas: 1
selector:
matchLabels:
app: app
template:
metadata:
labels:
app: app
name: app
spec:
containers:
- args:
- python3.9
- main.py
image: app
imagePullPolicy: Never
name: app
ports:
- name: app
containerPort: 8001
And service manifest for backend:
apiVersion: v1
kind: Service
metadata:
name: app-service
namespace: my-namespace
labels:
app: app-service
spec:
type: ClusterIP
ports:
- port: 8001
targetPort: app
selector:
app: app
My frontend deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: frontend-deployment
namespace: my-namespace
labels:
app: frontend
spec:
replicas: 1
selector:
matchLabels:
app: frontend
template:
metadata:
labels:
app: frontend
name: frontend
spec:
containers:
- args:
- python3.9
- -m
- uvicorn
- main:app
- --reload
- --port
- "8000"
- --host
- 0.0.0.0
image: frontend
imagePullPolicy: Never
name: frontend
ports:
- name: frontend
containerPort: 8000
Service for frontend:
apiVersion: v1
kind: Service
metadata:
name: frontend-service
namespace: my-namespace
labels:
app: frontend
spec:
type: ClusterIP
ports:
- protocol: TCP
port: 8000
targetPort: frontend
selector:
app: frontend
I have Ingress Controller (traefic) that routes traffic to cluster:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: traefik-ingress
namespace: my-namespace
annotations:
kubernetes.io/ingress.class: traefik
ingress.kubernetes.io/ssl-redirect: "false"
spec:
rules:
- host: my-dns.ca
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: frontend-service
port:
number: 8000
I changed the code in html in this way:
var ws = new WebSocket('ws://app-service.my-namespace.svc.cluster.local:8001');
but get ````Socket is closed. Reconnect will be attempted in 5 seconds... ```
How to get connection between services or debug connection?