Examine source code of SocketControl

{
  "description": "Control Firefox from a UNIX socket provided by a Native Messaging App.",
  "manifest_version": 2,
  "name": "SocketControl",
  "version": "1.5",
  "icons": {
    "48": "icons/app.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "native_control@karabaja4",
      "strict_min_version": "50.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/app.svg"
  },
  "permissions": [
    "nativeMessaging"
  ]
}