An article explaining in detail how to implement a port scanner in Go

This article brings you relevant knowledge about Go. It mainly introduces how to implement the port scanner in Go. There are code examples. Friends who are interested can take a look below. I hope it will be helpful to you.

Use GO to scan server ports in batches

1. Port scanner V1 - basic operation

package mainimport (
    "fmt"
    "net"
    "time"
    "unsafe")func main() {
    tcpScan("127.0.0.1", 1, 65535)}func tcpScan(ip string, portStart int, portEnd int) {
    start := time.Now()

    // 参数校验
    isok := verifyParam(ip, portStart, portEnd)
    if isok == false {
        fmt.Printf("[Exit]\n")
    }

    for i := portStart; i <= portEnd; i++ {
        address := fmt.Sprintf("%s:%d", ip, i)
        conn, err := net.Dial("tcp", address)
        if err != nil {
            fmt.Printf("[info] %s Close \n", address)
            continue
        }
        conn.Close()
        fmt.Printf("[info] %s Open \n", address)
    }

    cost := time.Since(start)
    fmt.Printf("[tcpScan] cost %s second \n", cost)}func verifyParam(ip string, portStart int, portEnd int) bool {
    netip := net.ParseIP(ip)
    if netip == nil {
        fmt.Println("[Error] ip type is must net.ip")
        return false
    }
    fmt.Printf("[Info] ip=%s | ip type is: %T | ip size is: %d \n", netip, netip, unsafe.Sizeof(netip))

    if portStart < 1 || portEnd > 65535 {
        fmt.Println("[Error] port is must in the range of 1~65535")
        return false
    }
    fmt.Printf("[Info] port start:%d end:%d \n", portStart, portEnd)

    return true}

2. Port scanner V2 - using goroutine

package mainimport (
    "fmt"
    "net"
    "sync"
    "time"
    "unsafe")func main() {
    tcpScanByGoroutine("127.0.0.1", 1, 65535)}func tcpScanByGoroutine(ip string, portStart int, portEnd int) {
    start := time.Now()
    // 参数校验
    isok := verifyParam(ip, portStart, portEnd)
    if isok == false {
        fmt.Printf("[Exit]\n")
    }

    var wg sync.WaitGroup    for i := portStart; i <= portEnd; i++ {
        wg.Add(1)

        go func(j int) {
            defer wg.Done()
            address := fmt.Sprintf("%s:%d", ip, j)
            conn, err := net.Dial("tcp", address)
            if err != nil {
                fmt.Printf("[info] %s Close \n", address)
                return
            }
            conn.Close()
            fmt.Printf("[info] %s Open \n", address)
        }(i)
    }
    wg.Wait()

    cost := time.Since(start)
    fmt.Printf("[tcpScanByGoroutine] cost %s second \n", cost)}func verifyParam(ip string, portStart int, portEnd int) bool {
    netip := net.ParseIP(ip)
    if netip == nil {
        fmt.Println("[Error] ip type is must net.ip")
        return false
    }
    fmt.Printf("[Info] ip=%s | ip type is: %T | ip size is: %d \n", netip, netip, unsafe.Sizeof(netip))

    if portStart < 1 || portEnd > 65535 {
        fmt.Println("[Error] port is must in the range of 1~65535")
        return false
    }
    fmt.Printf("[Info] port start:%d end:%d \n", portStart, portEnd)

    return true}

3. Port Scanner V3 - Using Goroutine Channel

package mainimport (
    "fmt"
    "net"
    "sync"
    "time"
    "unsafe")func main() {
    tcpScanByGoroutineWithChannel("127.0.0.1", 1, 65535)}func handleWorker(ip string, ports chan int, wg *sync.WaitGroup) {
    for p := range ports {
        address := fmt.Sprintf("%s:%d", ip, p)
        conn, err := net.Dial("tcp", address)
        if err != nil {
            fmt.Printf("[info] %s Close \n", address)
            wg.Done()
            continue
        }
        conn.Close()
        fmt.Printf("[info] %s Open \n", address)
        wg.Done()
    }}func tcpScanByGoroutineWithChannel(ip string, portStart int, portEnd int) {
    start := time.Now()

    // 参数校验
    isok := verifyParam(ip, portStart, portEnd)
    if isok == false {
        fmt.Printf("[Exit]\n")
    }

    ports := make(chan int, 100)
    var wg sync.WaitGroup    for i := 0; i < cap(ports); i++ {
        go handleWorker(ip, ports, &wg)
    }

    for i := portStart; i <= portEnd; i++ {
        wg.Add(1)
        ports <- i    }

    wg.Wait()
    close(ports)

    cost := time.Since(start)
    fmt.Printf("[tcpScanByGoroutineWithChannel] cost %s second \n", cost)}func verifyParam(ip string, portStart int, portEnd int) bool {
    netip := net.ParseIP(ip)
    if netip == nil {
        fmt.Println("[Error] ip type is must net.ip")
        return false
    }
    fmt.Printf("[Info] ip=%s | ip type is: %T | ip size is: %d \n", netip, netip, unsafe.Sizeof(netip))

    if portStart < 1 || portEnd > 65535 {
        fmt.Println("[Error] port is must in the range of 1~65535")
        return false
    }
    fmt.Printf("[Info] port start:%d end:%d \n", portStart, portEnd)

    return true}

4 Port Scanner V4 - Introducing two Channel

// packagepackage mainimport (
    "fmt"
    "net"
    "sort"
    "time"
    "unsafe")func main() {
    tcpScanByGoroutineWithChannelAndSort("127.0.0.1", 1, 65535)}// The function handles checking if ports are open or closed for a given IP address.func handleWorker(ip string, ports chan int, results chan int) {
    for p := range ports {
        address := fmt.Sprintf("%s:%d", ip, p)
        conn, err := net.Dial("tcp", address)
        if err != nil {
            // fmt.Printf("[debug] ip %s Close \n", address)
            results <- (-p)
            continue
        }
        // fmt.Printf("[debug] ip %s Open \n", address)
        conn.Close()
        results <- p    }}func tcpScanByGoroutineWithChannelAndSort(ip string, portStart int, portEnd int) {
    start := time.Now()

    // 参数校验
    isok := verifyParam(ip, portStart, portEnd)
    if isok == false {
        fmt.Printf("[Exit]\n")
    }

    ports := make(chan int, 50)
    results := make(chan int)
    var openSlice []int
    var closeSlice []int

    // 任务生产者-分发任务 (新起一个 goroutinue ，进行分发数据)
    go func(a int, b int) {
        for i := a; i <= b; i++ {
            ports <- i        }
    }(portStart, portEnd)

    // 任务消费者-处理任务  (每一个端口号都分配一个 goroutinue ，进行扫描)
    // 结果生产者-每次得到结果 再写入 结果 chan 中
    for i := 0; i < cap(ports); i++ {
        go handleWorker(ip, ports, results)
    }

    // 结果消费者-等待收集结果 (main中的 goroutinue 不断从 chan 中阻塞式读取数据)
    for i := portStart; i <= portEnd; i++ {
        resPort := <-results        if resPort > 0 {
            openSlice = append(openSlice, resPort)
        } else {
            closeSlice = append(closeSlice, -resPort)
        }
    }

    // 关闭 chan
    close(ports)
    close(results)

    // 排序
    sort.Ints(openSlice)
    sort.Ints(closeSlice)

    // 输出
    for _, p := range openSlice {
        fmt.Printf("[info] %s:%-8d Open\n", ip, p)
    }
    // for _, p := range closeSlice {
    //     fmt.Printf("[info] %s:%-8d Close\n", ip, p)
    // }

    cost := time.Since(start)
    fmt.Printf("[tcpScanByGoroutineWithChannelAndSort] cost %s second \n", cost)}func verifyParam(ip string, portStart int, portEnd int) bool {
    netip := net.ParseIP(ip)
    if netip == nil {
        fmt.Println("[Error] ip type is must net.ip")
        return false
    }
    fmt.Printf("[Info] ip=%s | ip type is: %T | ip size is: %d \n", netip, netip, unsafe.Sizeof(netip))

    if portStart < 1 || portEnd > 65535 {
        fmt.Println("[Error] port is must in the range of 1~65535")
        return false
    }
    fmt.Printf("[Info] port start:%d end:%d \n", portStart, portEnd)

    return true}

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