Port Scanner
To create a port scanner program in Go, you need to create a few files: main.go for the main logic and optionally, a scanner.go file for the scanning functionality. Here is a step-by-step guide:
Step 1: Initialize the Go Module
First, create a new directory for your project and initialize the Go module.
mkdir portscanner
cd portscanner
go mod init github.com/username/portscanner
Step 2: Create the scanner.go File
Create a scanner/portscanner.go file to handle the port scanning functionality.
// portscanner.go
package portscanner
import (
"fmt"
"net"
"time"
)
// ScanPort checks if a port is open on a given host.
func ScanPort(protocol, hostname string, port int) bool {
address := fmt.Sprintf("%s:%d", hostname, port)
conn, err := net.DialTimeout(protocol, address, 1*time.Second)
if err != nil {
return false
}
conn.Close()
return true
}
// ScanPorts scans a range of ports on a given host.
func ScanPorts(protocol, hostname string, startPort, endPort int) []int {
var openPorts []int
for port := startPort; port <= endPort; port++ {
if ScanPort(protocol, hostname, port) {
openPorts = append(openPorts, port)
}
}
return openPorts
}
Step 3: Create the main.go File
Create a main.go file to use the scanning functionality.
// main.go
package main
import (
"fmt"
"os"
"strconv"
portscanner "github.com/username/portscanner/scanner"
)
func main() {
if len(os.Args) != 5 {
fmt.Println("Usage: portscanner <protocol> <hostname> <startPort> <endPort>")
os.Exit(1)
}
protocol := os.Args[1]
hostname := os.Args[2]
startPort, err := strconv.Atoi(os.Args[3])
if err != nil {
fmt.Printf("Invalid start port: %v\n", err)
os.Exit(1)
}
endPort, err := strconv.Atoi(os.Args[4])
if err != nil {
fmt.Printf("Invalid end port: %v\n", err)
os.Exit(1)
}
openPorts := portscanner.ScanPorts(protocol, hostname, startPort, endPort)
if len(openPorts) == 0 {
fmt.Println("No open ports found.")
} else {
fmt.Printf("Open ports: %v\n", openPorts)
}
}
Step 4: Run the Program
Run the program using the go run command.
go run main.go tcp example.com 1 1024
This will scan the ports from 1 to 1024 on the specified host using the specified protocol and print the open ports.
Last modified: 08 January 2025