使用golang网络编程实现一个简单的TCP代理(不支持HTTP)
package main
import (
"flag"
"github.com/rs/zerolog"
"net"
"os"
)
var logger = zerolog.New(os.Stdout).With().Timestamp().Logger()
func main() {
help := flag.Bool("help", false, "print usage")
bind := flag.String("bind", "127.0.0.1:6000", "The address to bind to")
backend := flag.String("backend", "", "The backend server address")
flag.Parse()
logger.Level(zerolog.DebugLevel)
if *help {
flag.Usage()
return
}
if *backend == "" {
flag.Usage()
return
}
if *bind == "" {
//use default bind
logger.Info().Str("bind", *bind).Msg("use default bind")
}
success, err := RunProxy(*bind, *backend)
if !success {
logger.Error().Err(err).Send()
os.Exit(1)
}
}
func RunProxy(bind, backend string) (bool, error) {
listener, err := net.Listen("tcp", bind)
if err != nil {
return false, err
}
defer listener.Close()
logger.Info().Str("bind", bind).Str("backend", backend).Msg("tcp-proxy started.")
for {
conn, err := listener.Accept()
if err != nil {
logger.Error().Err(err).Send()
} else {
go ConnectionHandler(conn, backend)
}
}
}
func ConnectionHandler(conn net.Conn, backend string) {
logger.Info().Str("conn", conn.RemoteAddr().String()).Msg("client connected.")
target, err := net.Dial("tcp", backend)
defer conn.Close()
if err != nil {
logger.Error().Err(err).Send()
} else {
defer target.Close()
logger.Info().Str("conn", conn.RemoteAddr().String()).Str("backend", target.LocalAddr().String()).Msg("backend connected.")
closed := make(chan bool, 2)
go Proxy(conn, target, closed)
go Proxy(target, conn, closed)
<-closed
logger.Info().Str("conn", conn.RemoteAddr().String()).Msg("Connection closed.")
}
}
func Proxy(from net.Conn, to net.Conn, closed chan bool) {
buffer := make([]byte, 4096)
for {
n1, err := from.Read(buffer)
if err != nil {
closed <- true
return
}
n2, err := to.Write(buffer[:n1])
logger.Debug().Str("from", from.RemoteAddr().String()).Int("recv", n1).Str("to", to.RemoteAddr().String()).Int("send", n2).Send()
if err != nil {
closed <- true
return
}
}
}
使用方式
代理监听9000端口,代理后端服务的8000端口
tcp-proxy --bind 0.0.0.0:9000 --backend 127.0.0.1:8000
源码解析
这个简单的小程序主要由三个函数构成
1.RunProxy 启动代理服务,监听bind参数指定的端口,接收客户端请求
2.ConnectionHandler 客户端请求处理,连接backend服务
3.Proxy 数据传输代理,将客户端数据发送到backend服务,将backend数据发送给客户端
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