echo server

echo.go

package main

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

func echo(w http.ResponseWriter, r *http.Request) {
	u := r.URL
	resp := fmt.Sprintf(`Method: %s

Host: %s

Path: %s

Query: %s

Fragment: %s

Header: %s

Body: %s

ContentLength: %d

TransferEncoding: %s

RemoteAddr: %s`,
		r.Method,
		r.Host,
		u.Path,
		func() string {
			q, err := url.QueryUnescape(u.RawQuery)
			if err != nil {
				return u.RawQuery
			}
			return q
		}(),
		u.Fragment,
		r.Header,
		func() string {
			buf := new(bytes.Buffer)
			_, _ = buf.ReadFrom(r.Body)
			b := buf.String()
			q, err := url.QueryUnescape(b)
			if err != nil {
				return b
			}
			return q
		}(),
		r.ContentLength,
		r.TransferEncoding,
		func() string {
			ip := r.Header.Get("X-Real-IP")
			if ip != "" {
				return ip
			}
			ip = strings.Split(r.Header.Get("X-Forwarded-For"), ", ")[0]
			if ip != "" {
				return ip
			}
			return r.RemoteAddr
		}(),
	)

	_, _ = io.WriteString(w, resp)
}

func main() {
	http.HandleFunc("/", echo)
	fmt.Println(http.ListenAndServe("127.0.0.1:2323", nil))
}