Go Scripts to Scan TCP Ports

tcpscan.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"time"
)

var target = flag.String("target", "", "target to scan ports")

func main() {

	log.Println("start")
	defer log.Println("end")

	var open_ports []int

	flag.Parse()

	if *target == "" {
		log.Fatalln("no --target parameter providing for scanning")
	}

	for port := 1; port <= 1024; port++ {
		address := fmt.Sprintf("%s:%d", *target, port)
		conn, err := net.DialTimeout("tcp", address, 2*time.Second)
		if err != nil {
			if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
				log.Println("Connection timed out")
			} else {
				log.Println("Connection refused", neterr)
			}
		} else {
			conn.Close()
			log.Printf("Port %d is open on %s\n", port, address)
			open_ports = append(open_ports, port)
		}
	}

	for _, port := range open_ports {
		fmt.Printf("Address %s has Port:%d opened\n", *target, port)
	}
}

tcpscan_chan.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"sort"
	"time"
)

var target = flag.String("target", "", "target to scan ports")

func scanner(target string, ports, results chan int) {
	for port := range ports {
		address := fmt.Sprintf("%s:%d", target, port)
		conn, err := net.DialTimeout("tcp", address, 2*time.Second)
		if err != nil {
			neterr, ok := err.(net.Error)
			if ok && neterr.Timeout() {
				log.Println("Connection timed out")
			} else {
				log.Println("Connection refused", neterr)
			}
			results <- 0
		} else {
			conn.Close()
			results <- port
		}
	}
}

func main() {
	log.Println("start")
	defer log.Println("end")

	flag.Parse()

	if *target == "" {
		log.Fatalf("no --target parameter provided for scanning - aborting")
	}

	ports := make(chan int, 100)
	results := make(chan int)

	var open_ports []int

	for port := 1; port <= cap(ports); port++ {
		go scanner(*target, ports, results)
	}

	go func() {
		for port := 1; port <= 1024; port++ {
			ports <- port
		}
	}()

	for port := 1; port <= 1024; port++ {
		port_status := <-results
		if port_status != 0 {
			open_ports = append(open_ports, port_status)
		}
	}

	close(ports)
	close(results)
	sort.Ints(open_ports)
	for _, port := range open_ports {
		fmt.Printf("Address %s has Port:%d opened\n", *target, port)
	}
}

tcpscanport.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"time"
)

var target = flag.String("target", "", "target to scan")
var port = flag.Int("port", 80, "port to scan on remote host")

func main() {
	log.Println("start")
	defer log.Println("end")

	flag.Parse()

	if *target == "" {
		log.Fatalf("no --target parameter provided")
	}

	log.Printf("Connecting to %s:%d", *target, *port)
	conn, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%d", *target, *port), 2*time.Second)
	if err != nil {
		if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
			log.Println("Connection timed out")
		} else {
			log.Println("Connection refused", neterr)

		}
	} else {
		log.Println("Connection successful to", conn.RemoteAddr().String())
		conn.Close()
	}
}