Golang网络工具类整理

• 检测端口占用
  https://www.cnblogs.com/XiaoqiangCanFly/p/11820701.html

package main

import(
    "os/exec"
    "fmt"
)

func main(){
    fmt.Println(PortInUse(9001))
}

func PortInUse(port int) bool {
    checkStatement := fmt.Sprintf("lsof -i:%d ", port)
    output, _ := exec.Command("sh", "-c", checkStatement).CombinedOutput()
    if len(output) > 0 {
        return true
    }
    return false
}

• 获取外网ip地址
  https://transidc.com/?mod=support&type=detail&id=43 （仅用于测试）

https://httpbin.org/ip

• ipv4校验

package main

import (
    "fmt"
    "net"
)

func isValidIPv4(ip string) bool {
    return net.ParseIP(ip).To4() != nil
}

func main() {
    validIP := "192.168.1.1"
    invalidIP := "2001:0db8:85a3:0000:0000:8a2e:0370:7334"

    fmt.Printf("Is %s a valid IPv4 address? %t\n", validIP, isValidIPv4(validIP))
    fmt.Printf("Is %s a valid IPv4 address? %t\n", invalidIP, isValidIPv4(invalidIP))
}

• 判断http请求是从内网还是外网发起

package main

import (
    "fmt"
    "net"
    "net/http"
)

func isPrivateIP(ip net.IP) bool {
    if ip.IsLoopback() {
        return true
    }
    ip4 := ip.To4()
    if ip4 == nil {
        return false
    }
    return ip4[0] == 10 || // 10.x.x.x
        (ip4[0] == 172 && (ip4[1] >= 16 && ip4[1] <= 31)) || // 172.16.x.x - 172.31.x.x
        (ip4[0] == 192 && ip4[1] == 168) // 192.168.x.x
}

func handler(w http.ResponseWriter, r *http.Request) {
    ip := r.RemoteAddr
    if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
        ip = xff
    }
    host, _, err := net.SplitHostPort(ip)
    if err != nil {
        fmt.Fprintf(w, "Failed to parse IP: %v\n", err)
        return
    }
    if isPrivateIP(net.ParseIP(host)) {
        fmt.Fprintf(w, "Local IP Access\n")
    } else {
        fmt.Fprintf(w, "External IP Access\n")
    }
}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":8080", nil)
}

另外，可以根据http协议原理，从request的host字段中直接拿到请求的ip地址。