package main

import (
	"fmt"
	"net"
	"os"
	"strconv"
)

type ScanResult struct {
	Success bool
	Port int
	Err error
}

func scan(port int, host string) ScanResult {
	conn, err := net.Dial("tcp", fmt.Sprintf("%v:%v", host, port))
	result := ScanResult {
		Port: port,
		Success: err == nil,
		Err: err,
	}
	if conn != nil {
		conn.Close()
	}
	return result
}

func show_usage() {
	fmt.Println("USAGE: ./goscanner.exe <IP> <MIN_PORT> <MAX_PORT>")
}


func main() {
	args := os.Args

	if len(args) != 4 {
		show_usage()
		os.Exit(0)
	} else {
		min, _ := strconv.Atoi(args[2])
		max, _ := strconv.Atoi(args[3])
		for min <= max {
			if scan(min, args[1]).Success == true {
				fmt.Printf("OPEN %d\n", min)
			} else {
				fmt.Printf("CLOSED %d\n", min)
			}
			min += 1
		}
	}
}