Port Already in Use on Replit

1. Previous deployment process not fully stopped
2. Using hardcoded port instead of PORT environment variable
3. Multiple instances of app running simultaneously
4. Trying to bind to port < 1024 (requires root)
5. Different app using the same port

Always listen on the PORT environment variable instead of hardcoding (e.g., server.port=${PORT:8080}). Kill any lingering processes with pkill or restart the deployment. Ensure only one version of your app is running. Use ports >= 1024 for non-root processes.