goscanr

A fast, concurrent TCP port scanner written in Go.

Description

goscanr is a simple yet efficient port scanner that uses Go's concurrency features to scan multiple ports simultaneously. It can quickly identify open TCP ports on a target host within a specified range.

Features

• Fast concurrent scanning: Uses goroutines to scan multiple ports simultaneously
• Configurable port range: Specify start and end ports for scanning
• Adjustable timeout: Set connection timeout for port probes
• Simple CLI interface: Easy-to-use command-line flags
• Lightweight: Minimal dependencies, pure Go implementation

Installation

Prerequisites

• Go 1.24.7 or later

Build from source

git clone https://github.com/bvdwalt/goscanr.git
cd goscanr
go build -o goscanr main.go

Usage

Basic Usage

./goscanr -target <hostname_or_ip>

Advanced Usage

./goscanr -target <hostname_or_ip> -start <start_port> -end <end_port> -timeout <timeout_ms>

Command Line Options

Flag	Description	Default
-target	Target hostname or IP address (required)	-
-start	Starting port number	1
-end	Ending port number	1024
-timeout	Connection timeout in milliseconds	300

Examples

Scan common ports on localhost

./goscanr -target localhost

Scan a specific port range

./goscanr -target example.com -start 80 -end 443

Scan with custom timeout

./goscanr -target 192.168.1.1 -start 1 -end 65535 -timeout 1000

Quick scan of well-known ports

./goscanr -target target.example.com -start 20 -end 1024 -timeout 200

Sample Output

Scanning example.com from port 1 to 1024...
Port 22 is open
Port 53 is open
Port 80 is open
Port 443 is open
Scan complete.

How It Works

The scanner uses Go's net.DialTimeout() function to attempt TCP connections to each port in the specified range. Each port is scanned in a separate goroutine for maximum concurrency, with a sync.WaitGroup ensuring all scans complete before the program exits.

Performance Considerations

• Concurrency: The scanner creates one goroutine per port, which provides excellent performance but may be resource-intensive for very large port ranges
• Timeout: Lower timeout values increase scan speed but may miss slower-responding services
• Network limits: Very aggressive scanning may trigger rate limiting or be flagged by intrusion detection systems

Legal and Ethical Use

This tool is intended for:

• Testing your own systems and networks
• Authorized penetration testing and security assessments
• Educational purposes

Important: Only scan systems you own or have explicit permission to test. Unauthorized port scanning may violate terms of service, local laws, or regulations.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is open source. Please check the repository for license details.

Author

Created by bvdwalt