第 15 章 网络

package main

import (
	"fmt"
	"net"
)

func main() {
	fmt.Println("Starting the server ...")
	// 创建 listener
	listener, err := net.Listen("tcp", "localhost:50000")
	if err != nil {
		fmt.Println("Error listening", err.Error())
		return // 终止程序
	}
	// 监听并接受来自客户端的连接
	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Println("Error accepting", err.Error())
			return // 终止程序
		}
		go doServerStuff(conn)
	}
}

func doServerStuff(conn net.Conn) {
	for {
		buf := make([]byte, 512)
		len, err := conn.Read(buf)
		if err != nil {
			fmt.Println("Error reading", err.Error())
			return // 终止程序
		}
		fmt.Printf("Received data: %v", string(buf[:len]))
	}
}

package main

import (
	"bufio"
	"fmt"
	"net"
	"os"
	"strings"
)

func main() {
	// 打开连接:
	conn, err := net.Dial("tcp", "localhost:50000")
	if err != nil {
		// 由于目标计算机积极拒绝而无法创建连接
		fmt.Println("Error dialing", err.Error())
		return // 终止程序
	}

	inputReader := bufio.NewReader(os.Stdin)
	fmt.Println("First, what is your name?")
	clientName, _ := inputReader.ReadString('\n')
	// fmt.Printf("CLIENTNAME %s", clientName)
	trimmedClient := strings.Trim (clientName, "\r\n") // Windows 平台下用 "\r\n"，Linux 平台下使用 "\n"
	// 给服务器发送信息直到程序退出：
	for {
		fmt.Println("What to send to the server? Type Q to quit.")
		input, _ := inputReader.ReadString('\n')
		trimmedInput := strings.Trim(input, "\r\n")
		// fmt.Printf("input:--%s--", input)
		// fmt.Printf("trimmedInput:--%s--", trimmedInput)
		if trimmedInput == "Q" {
			return
		}
		_, err = conn.Write([]byte(trimmedClient + " says: " + trimmedInput))
	}
}

package main

import (
	"fmt"
	"log"
	"net/http"
)

func HelloServer(w http.ResponseWriter, req *http.Request) {
	fmt.Println("Inside HelloServer handler")
	fmt.Fprintf(w, "Hello,"+req.URL.Path[1:])
}

func main() {
	http.HandleFunc("/", HelloServer)
	err := http.ListenAndServe("localhost:8080", nil)
	if err != nil {
		log.Fatal("ListenAndServe: ", err.Error())
	}
}

package main

import (
	"fmt"
	"net/http"
)

var urls = []string{
	"http://www.google.com/",
	"http://golang.org/",
	"http://blog.golang.org/",
}

func main() {
	// Execute an HTTP HEAD request for all url's
	// and returns the HTTP status string or an error string.
	for _, url := range urls {
		resp, err := http.Head(url)
		if err != nil {
			fmt.Println("Error:", url, err)
		}
		fmt.Println(url, ": ", resp.Status)
	}
}

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
)

func main() {
	res, err := http.Get("http://www.google.com")
	checkError(err)
	data, err := ioutil.ReadAll(res.Body)
	checkError(err)
	fmt.Printf("Got: %q", string(data))
}

func checkError(err error) {
	if err != nil {
		log.Fatalf("Get : %v", err)
	}
}

package main

import (
	"net/http"
	"io/ioutil"
	"log"
	"regexp"
	"text/template"
)

const lenPath = len("/view/")

var titleValidator = regexp.MustCompile("^[a-zA-Z0-9]+$")
var templates = make(map[string]*template.Template)
var err error

type Page struct {
	Title string
	Body  []byte
}

func init() {
	for _, tmpl := range []string{"edit", "view"} {
		templates[tmpl] = template.Must(template.ParseFiles(tmpl + ".html"))
	}
}

func main() {
	http.HandleFunc("/view/", makeHandler(viewHandler))
	http.HandleFunc("/edit/", makeHandler(editHandler))
	http.HandleFunc("/save/", makeHandler(saveHandler))
	err := http.ListenAndServe("localhost:8080", nil)
	if err != nil {
		log.Fatal("ListenAndServe: ", err.Error())
	}
}

func makeHandler(fn func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		title := r.URL.Path[lenPath:]
		if !titleValidator.MatchString(title) {
			http.NotFound(w, r)
			return
		}
		fn(w, r, title)
	}
}

func viewHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := load(title)
	if err != nil { // page not found
		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
		return
	}
	renderTemplate(w, "view", p)
}

func editHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := load(title)
	if err != nil {
		p = &Page{Title: title}
	}
	renderTemplate(w, "edit", p)
}

func saveHandler(w http.ResponseWriter, r *http.Request, title string) {
	body := r.FormValue("body")
	p := &Page{Title: title, Body: []byte(body)}
	err := p.save()
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/view/"+title, http.StatusFound)
}

func renderTemplate(w http.ResponseWriter, tmpl string, p *Page) {
	err := templates[tmpl].Execute(w, p)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

func (p *Page) save() error {
	filename := p.Title + ".txt"
	// file created with read-write permissions for the current user only
	return ioutil.WriteFile(filename, p.Body, 0600)
}

func load(title string) (*Page, error) {
	filename := title + ".txt"
	body, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	return &Page{Title: title, Body: body}, nil
}