正向代理服务器

package main

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

/**
正向代理
*/
type Pxy struct{}

// 定义结构体 实现 ServeHTTP。就能把请求 传递到 http handle 里面
func (p *Pxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	fmt.Printf("Received request %s %s %s\n", req.Method, req.Host, req.RemoteAddr)
	
	transport := http.DefaultTransport // 数据链接词
	
	// step 1，浅拷贝对象，然后就再新增属性数据； 避免使用同一个 http，下文重定向是被影响
	outReq := new(http.Request)
	*outReq = *req
	if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
		if prior, ok := outReq.Header["X-Forwarded-For"]; ok {
			clientIP = strings.Join(prior, ", ") + ", " + clientIP
		}
		outReq.Header.Set("X-Forwarded-For", clientIP)	// X-Forwarded-For 设置远程代理 ip
	}

	// step 2, 请求下游
	res, err := transport.RoundTrip(outReq)
	if err != nil {
		rw.WriteHeader(http.StatusBadGateway)
		return
	}

	// step 3, 把下游请求内容返回给上游
	for key, value := range res.Header {
		for _, v := range value {
			rw.Header().Add(key, v)
		}
	}
	rw.WriteHeader(res.StatusCode)
	io.Copy(rw, res.Body)
	res.Body.Close()
}

func main() {
	fmt.Println("Serve on :8080")
	http.Handle("/", &Pxy{})
	http.ListenAndServe("0.0.0.0:8080", nil)
}
复制代码