Troubleshooting Center

Complete solutions for development environment problems and debugging issues

Development environments can be complex, and problems often arise that can slow down your workflow. This troubleshooting center provides comprehensive solutions for the most common development issues, organized by problem type for easy navigation and quick resolution.
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Interactive Problem Diagnostic Wizard

Answer a few questions to find the right solution for your issue

What type of problem are you experiencing?

Can't find what you're looking for? Browse all solutions below

🔍 Quick Problem Diagnosis

Not sure what's wrong? Start here to identify your issue:

🎓 Understand Core Concepts

Don't just fix errors—understand why they happen. Deep dives into networking, environment, and infrastructure.

🌐 IP Addresses Explained

Master IPv4, IPv6, Subnets, and why 127.0.0.1 is special.
Learn about loopback, LAN vs WAN, and CIDR.
Read Guide →

🔌 Networking for Developers

The missing manual on TCP, UDP, Sockets, and Protocols.
Understand the OSI model and 3-way handshakes.
Read Guide →

🔑 Environment Variables

Secure your secrets and manage config with .env files.
Stop hardcoding API keys and database passwords.
Read Guide →

🐳 Docker Networking

Fix container communication issues and port mapping errors.
Understand bridges, hosts, and internal DNS.
Read Guide →

🚪 Port Issues

Problems related to port conflicts, port already in use, and port configuration.

🚫 Port Already in Use

Your application can't start because the port is already occupied by another process.
Error: "Port XXXX is already in use" or "Address already in use"
View Complete Solution →

⚙️ Port Configuration Problems

Issues with port configuration in different frameworks and environments.
Server starts on wrong port, can't change default port
View Port Configuration Guide →

🔌 Connection Issues

Network connectivity problems, connection refused errors, and localhost access issues.

❌ Connection Refused

Unable to connect to localhost or specific services due to network issues.
"Connection refused", "ERR_CONNECTION_REFUSED"
View Complete Solution →

🏠 Localhost Not Working

Localhost access problems and development server connectivity issues.
"This site can't be reached", "localhost refused to connect"
View Complete Solution →

🌐 DNS Resolution Issues

Problems with localhost DNS resolution and hosts file configuration.
"DNS_PROBE_FINISHED_NXDOMAIN", "ERR_NAME_NOT_RESOLVED"
View DNS Troubleshooting →

🌐 Browser Issues

Cross-origin problems, browser cache issues, and frontend development problems.

🚫 CORS Errors

Cross-origin resource sharing issues preventing API calls from frontend.
"CORS policy", "Access-Control-Allow-Origin" errors
View Complete Solution →

💾 Browser Cache Problems

Stale cache causing issues with local development and testing.
Old versions showing, changes not reflecting
View Cache Troubleshooting →

🗄️ Database Issues

Database connection problems, configuration issues, and data access errors.

🐬 MySQL Connection Issues

Problems connecting to MySQL database on port 3306.
"Can't connect to MySQL server", "Access denied"
View MySQL Troubleshooting →

🐘 PostgreSQL Connection Issues

Problems connecting to PostgreSQL database on port 5432.
"Connection to server failed", "Authentication failed"
View PostgreSQL Troubleshooting →

🍃 MongoDB Connection Issues

Problems connecting to MongoDB database on port 27017.
"ECONNREFUSED", "MongoNetworkError"
View MongoDB Troubleshooting →

🔴 Redis Connection Issues

Problems connecting to Redis cache on port 6379.
"Connection refused", "Redis connection failed"
View Redis Troubleshooting →

⚙️ Framework-Specific Issues

Problems specific to popular development frameworks and technologies.

⚛️ React Development Issues

Common problems in React development and debugging.
Hooks errors, state issues, performance problems
View React Troubleshooting →

🍃 Spring Boot Issues

Common problems in Spring Boot application development.
Startup failures, dependency injection, database issues
View Spring Boot Troubleshooting →

🛠️ Development Environment Setup

Comprehensive guides for setting up and configuring development environments.

Development Environment Configuration Guide

Complete setup guide for local development environments, port management, and server configuration.

  • Frontend Development Ports (3000, 5173, 4200)
  • Backend Development Ports (8080, 8000, 5000)
  • Database Ports (3306, 5432, 27017, 6379)
  • Framework-Specific Configurations
  • Best Practices and Security Considerations
View Complete Configuration Guide →

🛡️ Prevention and Best Practices

Proactive Troubleshooting:
  • Use consistent port ranges for different service types
  • Document your development environment setup
  • Implement health checks for critical services
  • Keep development dependencies updated
  • Use environment variables for configuration
Debugging Strategies:
  • Start with the simplest possible setup
  • Check logs and error messages carefully
  • Use network diagnostic tools (ping, telnet, curl)
  • Test with different browsers and tools
  • Isolate the problem by testing components separately
Learning Resources:
  • Understand the fundamentals of networking and ports
  • Learn about your framework's configuration options
  • Familiarize yourself with common error messages
  • Keep up with best practices in your technology stack

🚨 Emergency Quick Fixes

When All Else Fails:
  • Restart everything: Your computer, development server, database
  • Clear all caches: Browser cache, npm cache, application cache
  • Check system resources: CPU, memory, disk space
  • Use a different port: Change to an unused port number
  • Try a different browser: Test in incognito/private mode
  • Disable security software temporarily: Firewall, antivirus

Related Resources

External Resources