前话

最近痴迷于Golang这个新兴语言，因为它是强类型编译型语言，可以直接编译成三大平台的二进制执行文件，可以直接运行无需其他依赖环境。而且Golang独特的goroutine使得多线程任务执行如new一个对象般简单。

带着为学习理解Golang的好奇心情，我试着写了个端口扫描器。

github项目链接如下， 更多的实用工具我会慢慢添加。

源码

package mainimport (    "flag"    "fmt"    "net"    "os"    "regexp"    "strconv"    "strings"    "sync")var port intvar portRange stringvar parallelCounts intfunc init() {    flag.IntVar(&port, "p", 80, "port")    flag.StringVar(&portRange, "r", "", "range ports. format is 
    
     ~
     
      . eg. 100~200")    flag.IntVar(&parallelCounts, "n", 1, "parallel counts")    // 修改提示信息    flag.Usage = func() {        fmt.Fprintf(os.Stderr, "\nUsage: %s [Options] 
      
       \n\nOptions:\n\n", os.Args[0])        flag.PrintDefaults()    }    flag.Parse()}func printOpeningPort(port int) {    fmt.Println("port " + strconv.Itoa(port) + " is opening")}func checkPort(ip net.IP, port int, wg *sync.WaitGroup, parallelChan *chan int) {    defer wg.Done()    tcpAddr := net.TCPAddr{        IP:   ip,        Port: port,    }    conn, err := net.DialTCP("tcp", nil, &tcpAddr)    if err == nil {        printOpeningPort(port)        conn.Close()    }    <-*parallelChan}func main() {    args := flag.Args()    if len(args) != 1 {        flag.Usage()    } else {        ip := net.ParseIP(flag.Arg(0))        // 用于协程任务控制        wg := sync.WaitGroup{}        if portRange != "" {            matched, _ := regexp.Match(`^\d+~\d+$`, []byte(portRange))            if !matched {                flag.Usage()            } else {                portSecs := strings.Split(portRange, "~")                startPort, err1 := strconv.Atoi(portSecs[0])                endPort, err2 := strconv.Atoi(portSecs[1])                if err1 != nil || err2 != nil || startPort < 1 || endPort < 2 || endPort <= startPort || parallelCounts < 1 {                    flag.Usage()                } else {                    wg.Add(endPort - startPort + 1)                    // 用于控制协程数                    parallelChan := make(chan int, parallelCounts)                    for i := startPort; i <= endPort; i++ {                        parallelChan <- 1                        go checkPort(ip, i, &wg, &parallelChan)                    }                    wg.Wait()                }            }        } else {            wg.Add(1)            parallelChan := make(chan int)            go func() {                parallelChan <- 1            }()            go checkPort(ip, port, &wg, &parallelChan)            wg.Wait()        }    }}
      
     
    

运行结果

1. 执行 go build ./main.go， 生成二进制文件

2. 运行二进制文件，结果如下：

   ```
   $ port-scanner.exe

   Usage: E:\Program Files\GoPath\bin\port-scanner.exe [Options]

   Options:

   -n int

   parallel counts (default 1)
   -p int
   port (default 80)
   -r string
   range ports. format is ~. eg. 100~200

   $ port-scanner.exe -p 80 127.0.0.1

   port 80 is opening

   $ port-scanner.exe -r 1~100 -n 50 127.0.0.1

   port 80 is opening
   ```