Testing a webapplication in Docker Desktop without internet access

compose.yml

# Open a web browser from a web browser
# curl localhost:3000
networks:
  default:
    internal: true
  public:

services:
  php:
    image: itsziget/phar-examples:1.0

  firefox:
    network_mode: service:php
    environment:
      PUID: 1000
      PGID: 1000
      TZ: Europe/London
    shm_size: "1gb"
    image: lscr.io/linuxserver/firefox:101.0.1

  proxy:
    image: alpine/socat:1.7.4.4-r0
    command: "TCP-LISTEN:3000,fork,reuseaddr TCP:php:3000"
    ports:
      - 3000:3000
    networks:
      - default
      - public