netcheck

A powerful bash-based network connectivity testing tool that supports:

Core Testing Features:
- ICMP ping testing with statistics and URL support
- DNS lookup with multiple fallback methods (accepts URLs)
- TCP port connectivity testing with parallel processing
- HTTP/HTTPS status code checking with performance metrics
- SSL/TLS certificate validation with expiry warnings

Network Diagnostics (v1.2.0):
- Show network interfaces with IP addresses (--my-ip)
- Retry failed connections with configurable count and delay
- HTTP status codes with response time and content size
- SSL certificate expiry check with advance warnings

Advanced Features:
- Parallel TCP connection testing (up to 256 concurrent jobs)
- Quick mode parallel processing for wide IP ranges
- Output file support for quick mode results (-o flag)
- IP range support (192.168.1.1-50)
- CIDR notation (10.0.0.0/24)
- Port ranges (8000-8100) and multiple ports (80,443,3306)
- CSV file input for bulk testing
- Multiple output formats (text, JSON, CSV, XML)
- Comprehensive input validation with helpful warnings
- Real-time progress tracking
- Combined reports with dated filenames

Perfect for:
- System administrators monitoring infrastructure
- DevOps engineers validating deployments
- Network diagnostics and troubleshooting
- DNS resolution verification
- ICMP connectivity testing
- HTTP/HTTPS status monitoring
- SSL certificate expiry tracking
- Security auditing and port scanning
- Load balancer health checks

IMPORTANT: For full functionality, run after installation:

 sudo snap connect netcheck:network-observe

This connection enables:
- ICMP ping tests (-p/--ping flag)
- Network interface information (--my-ip flag)

Without this connection, features like TCP port tests, DNS lookup, HTTP
status checks, SSL certificate validation, and retry logic work normally.