Speed Up The Script

Getting Help Code Review
#1

Hi , I am new to golang and joined this forum today.

I was writing the TCP scanner and just want to know is there anyway to speed up the script like really fast?

Now , it is so slow .

Below is my script

func main() {
	var hostName string
	var concurrency int

	logo()
	flag.StringVar(&hostName, "i" , "" , "Run with your hostname or IP")
	flag.IntVar(&concurrency , "c" , 50 , "Set the concurrency for greater speed")
	flag.Parse()


	var wg sync.WaitGroup
	for i:=0; i<= concurrency; i++ {
		wg.Add(1)
		go func () {
			Fullscan(hostName)
			wg.Done()
		}()
		wg.Wait()
	}
}

func Fullscan(hostName string) {
	for i := 1; i <= 65535; i++ {
		address := hostName + ":" + strconv.Itoa(i)
		conn, err := net.DialTimeout("tcp" , address , 60*time.Second)
		if err == nil {
			fmt.Println("Port" , strconv.Itoa(i)+"/open")
			conn.Close()
		}
	}
}
#2

Instead of having a single go routine per host, split even further . Have 10, 20, 40, whatever number of “workers” and send them a job item via channel from the main loop. That Job Item would contain host and port to scan.

1 Like
#3

Hi , thanks for the suggestion. I will try that out and research but I am a little bit confuse about the workers because I am new to golang.

#4

What exactly confuses you about the workers?

#5

I didn’t do it in past , I just write all with go routine and thanks for that. Will try it.

#6

I just realise, that you currently do not even do a go routine per host, but you start concurrency go routines, each doing a full scan of the same host.

#7

Oops I think I got you . Thanks.

#8

The following runs within ~5 seconds on my machine:

package main

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

type portResult struct {
	port int
	open bool
}

func main() {
	var hostName string
	var concurrency int

	flag.StringVar(&hostName, "i", "", "Give hostname or IP")
	flag.IntVar(&concurrency, "c", 10, "set number of concurrent scans")
	flag.Parse()

	var chIn chan int = make(chan int)
	var chOut chan portResult = make(chan portResult)

	for i := 0; i < concurrency; i++ {
		go runner(i, hostName, chIn, chOut)
	}

	go func() {
		for p := 1; p <= 0xffff; p++ {
			chIn <- p
		}
	}()

	for r := 1; r <= 0xffff; r++ {
		info := <-chOut

		if info.open {
			fmt.Printf("Port %v is open\n", info.port)
		}
	}

	close(chIn)
	close(chOut)
}

func runner(id int, host string, ports <-chan int, results chan<- portResult) {
	for p := range ports {
		fmt.Fprintf(os.Stderr, "%d: scanning port %v\n", id, p)
		address := fmt.Sprintf("%s:%d", host, p)
		conn, err := net.DialTimeout("tcp", address, time.Minute)
		if err != nil {
			results <- portResult{
				port: p,
				open: false,
			}
			continue
		}

		results <- portResult{
			port: p,
			open: true,
		}
		conn.Close()
	}
}

$ time go run . -i localhost -c 100 | tee ports.txt
[…]
go run . -i localhost -c 100  4.81s user 5.32s system 269% cpu 3.755 total
tee ports.txt  0.00s user 0.00s system 0% cpu 3.755 total

It results on 24 lines beeing printed to stdout, this corresponds with the number of services running on my machine and beeing bound to the loopback interface.

Please be also aware, that on my machine, there was no noticeable speed up after a concurrency of 4. Wall clock time was between 4.5 and 5 seconds for 4, 5, 10 and 100.

1 Like
#9

I will test it . Thanks for helping me! I am thinking about running on my VPS.

#10

Damm , that works really well even on my machine and thanks for helping me out!