Replit
deployment
Port Already in Use on Replit
Your app fails to start with 'Address already in use' or 'bind: permission denied' error. The port is already bound by another process.
Replit may have lingering processes from previous deployments still listening on the port.
Error Messages You Might See
Address already in use
Bind: permission denied
port 8080 is in use
ERROR: Address already in use (Os { code: 48
Common Causes
- Previous deployment process not fully stopped
- Using hardcoded port instead of PORT environment variable
- Multiple instances of app running simultaneously
- Trying to bind to port < 1024 (requires root)
- Different app using the same port
How to Fix It
Always listen on the PORT environment variable instead of hardcoding (e.g., server.port=${PORT:8080}). Kill any lingering processes with pkill or restart the deployment. Ensure only one version of your app is running. Use ports >= 1024 for non-root processes.
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Get HelpFrequently Asked Questions
How do I use the PORT environment variable?
In Spring Boot: server.port=${PORT:8080}. The :8080 is a fallback for local testing
How do I kill a process on Replit?
Use 'kill <pid>' or 'pkill -f processname' in the shell