scanport

A fast, multi-threaded TCP/UDP port scanner written in Go.

Table of Contents

• Features
• Requirements
• Installation
• Usage
• Options
• Examples
• Sample Output
• Troubleshooting
• License

Features

• Scan TCP and UDP ports simultaneously
• Scan multiple hosts in a single command
• Accepts both hostnames and IP addresses (with automatic reverse DNS lookup)
• Configurable connection timeout and worker thread count
• Color-coded output: open ports in green, closed ports in red
• Concurrent scanning via goroutines for maximum speed

Requirements

• Go 1.13+

Installation

Install directly with go install:

go install github.com/Dapacruz/scanport@latest

The binary will be placed in your $GOPATH/bin (or $HOME/go/bin by default). Make sure that directory is in your $PATH.

Alternatively, build from source:

git clone https://github.com/Dapacruz/scanport.git
cd scanport
go build -o scanport .

Usage

scanport -host <host[,host...]> [-tcp <port[,port...]>] [-udp <port[,port...]>] [options]

At least one -host and one port flag (-tcp or -udp) are required.

Options

Flag	Default	Description
-host	—	Comma-separated list of hostnames and/or IP addresses to scan
-tcp	—	Comma-separated list of TCP ports to scan
-udp	—	Comma-separated list of UDP ports to scan
-t	1	Connection timeout in seconds
-w	100	Maximum number of concurrent worker threads

Examples

Scan a single host for common web ports over TCP:

scanport -host www.example.com -tcp 80,443

Scan multiple IP addresses for a UDP port:

scanport -host 8.8.8.8,8.8.4.4 -udp 53

Scan multiple hosts for both TCP and UDP ports with a custom timeout:

scanport -host www.google.com,www.vmware.com -tcp 80,443 -udp 53 -t 5

Reduce concurrency to avoid connection limits:

scanport -host 192.168.1.1 -tcp 22,80,443,8080 -w 10

Sample Output

Scanning ports ...

93.184.216.34 (www.example.com) ==> TCP/80 is open
93.184.216.34 (www.example.com) ==> TCP/443 is open

Scan complete: 1 host(s) scanned in 0.243 seconds

Open ports are printed in green and closed ports in red.

Troubleshooting

too many open files error This occurs when the number of concurrent connections exceeds your OS's open file descriptor limit. Lower the worker count with -w:

scanport -host <target> -tcp <ports> -w 20

You can also raise the system limit temporarily:

ulimit -n 4096

Host cannot be resolved Ensure the hostname is spelled correctly and that your DNS is reachable. You can also pass an IP address directly with -host.

UDP scan results are unreliable UDP is a connectionless protocol. A port reported as "closed" means no response was received within the timeout window — this can be a false negative due to firewalls or packet loss. Increase the timeout with -t for more reliable results:

scanport -host <target> -udp 53 -t 5

License

This project is licensed under the MIT License.