Next.js inlines NEXT_PUBLIC_* variables into the JavaScript bundle at build time, not at runtime. NEXT_PUBLIC_SOCKET_URL is therefore baked into the client image when it is built. Setting or changing it in a running container has no effect.
After changing the URL, rebuild the client
docker compose build client
docker compose up -d
Forgetting to rebuild after changing NEXT_PUBLIC_SOCKET_URL is the most common reason a self-hosted Floe instance cannot connect to the signaling server.
The URL must be reachable by end-users’ browsers
NEXT_PUBLIC_SOCKET_URL is evaluated in the browser, not on the server. http://localhost:3001 only works when the browser runs on the same machine as the server. For any other setup, use the server’s LAN IP or public domain (e.g. https://api.your-domain.com). 
