一个简单的Golang实现的HTTP Proxy方法

package main

import (
  "bytes"
  "fmt"
  "io"
  "log"
  "net"
  "net/url"
  "strings"
)

func main() {
  log.SetFlags(log.LstdFlags|log.Lshortfile)
  l, err := net.Listen("tcp", ":8081")
  if err != nil {
    log.Panic(err)
  }

  for {
    client, err := l.Accept()
    if err != nil {
      log.Panic(err)
    }

    go handleClientRequest(client)
  }
}

func handleClientRequest(client net.Conn) {
  if client == nil {
    return
  }
  defer client.Close()

  var b [1024]byte
  n, err := client.Read(b[:])
  if err != nil {
    log.Println(err)
    return
  }
  var method, host, address string
  fmt.Sscanf(string(b[:bytes.IndexByte(b[:], '
')]), "%s%s", &method, &host)
  hostPortURL, err := url.Parse(host)
  if err != nil {
    log.Println(err)
    return
  }

  if hostPortURL.Opaque == "443" { //https访问
    address = hostPortURL.Scheme + ":443"
  } else { //http访问
    if strings.Index(hostPortURL.Host, ":") == -1 { //host不带端口， 默认80
      address = hostPortURL.Host + ":80"
    } else {
      address = hostPortURL.Host
    }
  }

  //获得了请求的host和port，就开始拨号吧
  server, err := net.Dial("tcp", address)
  if err != nil {
    log.Println(err)
    return
  }
  if method == "CONNECT" {
    fmt.Fprint(client, "HTTP/1.1 200 Connection established
")
  } else {
    server.Write(b[:n])
  }
  //进行转发
  go io.Copy(server, client)
  io.Copy(client, server)
}