http_echo_build.sh

#!/usr/bin/env bash
# 可以通过命令 go env 获取当前的环境变量
CGO_ENABLED=0 GOOS=linux   GOARCH=amd64 go build -ldflags "-s -w" -o http_echo_linux
CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build -ldflags "-s -w" -o http_echo_windows.exe
CGO_ENABLED=0 GOOS=darwin  GOARCH=amd64 go build -ldflags "-s -w" -o http_echo_mac

http_echo_main.go

package main

import (
	"flag"
	"log"
	"net"
	"os"
	"regexp"
	"strconv"
	"strings"
)

var p = flag.Int("p", 6728, "port")

const (
	frame = 256
	crLf2 = "\r\n\r\n"
)

var contentLengthReg = regexp.MustCompile(`content-length: *(\d+)\r\n`)

func getContentLength(request string) (length int) {
	request = strings.ToLower(request)
	params := contentLengthReg.FindStringSubmatch(request)
	if params != nil {
		value, err := strconv.Atoi(params[1])
		if err != nil {
			log.Fatalln(err)
		}
		length = value
	}
	return
}

func handleRequest(conn net.Conn) {
	// 不断地接受HTTP请求
	for {
		var contentLength int
		data := make([]byte, 0, frame*4)
		tmp := make([]byte, frame)
		// 读取HTTP请求报文
		for {
			length, err := conn.Read(tmp)
			// 连接断开
			if length == 0 {
				log.Println("Remove", conn.RemoteAddr().String())
				return
			}
			if err != nil {
				log.Fatalln("Error reading:", err)
			}
			data = append(data, tmp[:length]...)

			request := string(data)
			if strings.Contains(request, crLf2) {
				if contentLength == 0 {
					contentLength = getContentLength(request)
					if contentLength == 0 {
						break
					}
				}
				body := strings.Split(request, crLf2)[1]
				if len([]byte(body)) == contentLength {
					break
				}
			}
		}

		log.Println(string(data))
		head := []byte("HTTP/1.1 200 OK\r\n")
		head = append(head, []byte("content-length: "+strconv.Itoa(len(data))+"\r\n")...)
		head = append(head, []byte("content-type: text/plain"+crLf2)...)
		data = append(head, data...)
		conn.Write(data)
	}
}

func main() {
	log.SetOutput(os.Stdout)
	flag.Parse()
	port := strconv.Itoa(*p)

	listener, err := net.Listen("tcp", "0.0.0.0:"+port)
	if err != nil {
		log.Fatalln("Error listening:", err)
	}
	log.Println("Listening 0.0.0.0:" + port)
	defer listener.Close()

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Fatalln("Error accepting:", err)
		}
		log.Println("Accept", conn.RemoteAddr().String())
		go handleRequest(conn)
	}
}