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.
Real developers can help you.
Victor Denisov
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Richard McSorley
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I am a Strategic Engineering Leader with over 8 years of experience building high-availability enterprise systems and scaling high-performing technical teams. My focus is on bridging the gap between complex technology and business growth.
Core Expertise:
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I thrive on "out-of-the-box" thinking to solve complex technical bottlenecks and am always looking for ways to use automation to improve business productivity.
Matthew Jordan
I've been working at a large software company named Kainos for 2 years, and mainly specialise in Platform Engineering. I regularly enjoy working on software products outside of work, and I'm a huge fan of game development using Unity. I personally enjoy Python & C# in my spare time, but I also specialise in multiple different platform-related technologies from my day job.
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I am a technologist and product builder dedicated to creating high-impact solutions at the intersection of AI and specialized markets. Currently, I am focused on PropScan (EstateGuard), an AI-driven SaaS platform tailored for the Japanese real estate industry, and exploring the potential of Archify.
As an INFJ-T, I approach development with a "systems-thinking" mindset—balancing technical precision with a deep understanding of user needs. I particularly enjoy the challenge of architecting Vertical AI SaaS and optimizing Small Language Models (SLMs) to solve specific, real-world business problems. Whether I'm in a CTO-level leadership role or hands-on with the code, I thrive on building tools that turn complex data into actionable value.
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Yovel Cohen
I got a lot of experience in building Long-horizon AI Agents in production, Backend apps that scale to millions of users and frontend knowledge as well.
Milan Surelia
Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems.
Expertise:
💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web.
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Notable Achievements:
🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX.
🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development.
🌟 Open source contributions on Github & StackOverflow for Flutter & Dart
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Milan is always happy to connect, work on new ideas, and explore the latest in technology.
Pratik
SWE with 15+ years of experience building and maintaining web apps and extensive BE infrastructure
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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