Go语言学习笔记（六）net & net/http

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net

import "net"

net包提供了可移植的网络I/O接口，包括TCP/IP、UDP、域名解析和Unix域socket。

虽然本包提供了对网络原语的访问，大部分使用者只需要Dial、Listen和Accept函数提供的基本接口；以及相关的Conn和Listener接口。crypto/tls包提供了相同的接口和类似的Dial和Listen函数。

Listen函数创建的服务端：

ln, err := net.Listen("tcp", ":8080")
if err != nil {
// handle error
}
for {
conn, err := ln.Accept()
if err != nil {
// handle error
continue
}
go handleConnection(conn)
}

Dial函数和服务端建立连接：

conn, err := net.Dial("tcp", "google.com:80")
if err != nil {
// handle error
}
fmt.Fprintf(conn, "GET / HTTP/1.0\r\n\r\n")
status, err := bufio.NewReader(conn).ReadString('\n')
// ...

TCPConn

TCPConn代表一个TCP网络连接，实现了Conn接口。

Conn接口

Conn接口代表通用的面向流的网络连接。多个线程可能会同时调用同一个Conn的方法。

type Conn interface {
// Read从连接中读取数据
// Read方法可能会在超过某个固定时间限制后超时返回错误，该错误的Timeout()方法返回真
Read(b []byte) (n int, err error)
// Write从连接中写入数据
// Write方法可能会在超过某个固定时间限制后超时返回错误，该错误的Timeout()方法返回真
Write(b []byte) (n int, err error)
// Close方法关闭该连接
// 并会导致任何阻塞中的Read或Write方法不再阻塞并返回错误
Close() error
// 返回本地网络地址
LocalAddr() Addr
// 返回远端网络地址
RemoteAddr() Addr
// 设定该连接的读写deadline，等价于同时调用SetReadDeadline和SetWriteDeadline
// deadline是一个绝对时间，超过该时间后I/O操作就会直接因超时失败返回而不会阻塞
// deadline对之后的所有I/O操作都起效，而不仅仅是下一次的读或写操作
// 参数t为零值表示不设置期限
SetDeadline(t time.Time) error
// 设定该连接的读操作deadline，参数t为零值表示不设置期限
SetReadDeadline(t time.Time) error
// 设定该连接的写操作deadline，参数t为零值表示不设置期限
// 即使写入超时，返回值n也可能>0，说明成功写入了部分数据
SetWriteDeadline(t time.Time) error
}

栗子一(tcp)

tcp服务端

package main

import (
"fmt"
"net"
)

func process(conn net.Conn) {
defer conn.Close()
for {
buf := make([]byte, 512)
n, err := conn.Read(buf)
if err != nil {
fmt.Println("read err:", err)
return
}
fmt.Println("read:", string(buf[:n]))
}
}

func main() {
fmt.Println("server start...")
listen, err := net.Listen("tcp", "0.0.0.0:8000")
if err != nil {
fmt.Println("listen failed, err:", err)
return
}
for {
conn, err := listen.Accept()
if err != nil {
fmt.Println("accept failed, err:", err)
continue
}
go process(conn)
}
}

tcp客户端

package main

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

func main() {
conn, err := net.Dial("tcp", "localhost:8000")
if err != nil {
fmt.Println("err dialing:", err.Error())
return
}
defer conn.Close()
inputReader := bufio.NewReader(os.Stdin)
for {
input, _ := inputReader.ReadString('\n')
trimedInput := strings.Trim(input, "\r\n")
if trimedInput == "Q" {
return
}
_, err := conn.Write([]byte(trimedInput))
if err != nil {
fmt.Println("err conn.write:", err)
return
}
}
}

栗子二（http）

封装一个http连接，请求百度

package main

import (
"fmt"
"io"
"net"
)

func main() {
conn, err := net.Dial("tcp", "www.baidu.com:80")
if err != nil {
fmt.Println("err dialing:", err.Error())
return
}
defer conn.Close()

msg := "GET / HTTP/1.1\r\n"
msg += "Host: www.baidu.com\r\n"
msg += "Connection: close\r\n"
// msg += "Connection: keep-alive\r\n"
msg += "\r\n\r\n"

_, err = io.WriteString(conn, msg)
if err != nil {
fmt.Println("io write string failed, err:", err)
return
}
buf := make([]byte, 4096)
for {
count, err := conn.Read(buf)
if err != nil {
break
}
fmt.Println(string(buf[:count]))
}
}

net/http

import "net/http"

http包提供了HTTP客户端和服务端的实现。

Get、Head、Post和PostForm函数发出HTTP/ HTTPS请求。

resp, err := http.Get("http://example.com/")
...
resp, err := http.Post("http://example.com/upload", "image/jpeg", &buf)
...
resp, err := http.PostForm("http://example.com/form",
url.Values{"key": {"Value"}, "id": {"123"}})

程序在使用完回复后必须关闭回复的主体。

resp, err := http.Get("http://example.com/")
if err != nil {
// handle error
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
// ...

要管理HTTP客户端的头域、重定向策略和其他设置，创建一个Client：

client := &http.Client{
CheckRedirect: redirectPolicyFunc,
}
resp, err := client.Get("http://example.com")
// ...
req, err := http.NewRequest("GET", "http://example.com", nil)
// ...
req.Header.Add("If-None-Match", `W/"wyzzy"`)
resp, err := client.Do(req)
// ...

要管理代理、TLS配置、keep-alive、压缩和其他设置，创建一个Transport：

tr := &http.Transport{
TLSClientConfig:    &tls.Config{RootCAs: pool},
DisableCompression: true,
}
client := &http.Client{Transport: tr}
resp, err := client.Get("https://example.com")

Client和Transport类型都可以安全的被多个go程同时使用。出于效率考虑，应该一次建立、尽量重用。

ListenAndServe使用指定的监听地址和处理器启动一个HTTP服务端。处理器参数通常是nil，这表示采用包变量DefaultServeMux作为处理器。Handle和HandleFunc函数可以向DefaultServeMux添加处理器。

http.Handle("/foo", fooHandler)
http.HandleFunc("/bar", func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
})
log.Fatal(http.ListenAndServe(":8080", nil))

要管理服务端的行为，可以创建一个自定义的Server：

s := &http.Server{
Addr:           ":8080",
Handler:        myHandler,
ReadTimeout:    10 * time.Second,
WriteTimeout:   10 * time.Second,
MaxHeaderBytes: 1 << 20,
}
log.Fatal(s.ListenAndServe())

栗子server

import (
"fmt"
"net/http"
)

func Hello(w http.ResponseWriter, r *http.Request) {
fmt.Println("Hello World.")
fmt.Fprintf(w, "Hello World.\n")
}

func main() {
http.HandleFunc("/", Hello)
err := http.ListenAndServe("0.0.0.0:6000", nil)
if err != nil {
fmt.Println("http listen failed.")
}
}

栗子client

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

func main() {
res, err := http.Get("http://www.baidu.com")
if err != nil {
fmt.Println("Get error:", err)
return
}

data, err := ioutil.ReadAll(res.Body)
if err != nil {
fmt.Println("Get data error:", err)
return
}

fmt.Println(string(data))
}

栗子head

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

var url = []string{
"http://www.baidu.com",
"http://www.google.com",
"http://pan.263.net",
}

func main() {
for _, v := range url {
http.DefaultClient.Timeout = time.Second * 2
resp, err := http.Head(v)
if err != nil {
fmt.Printf("head %s failed, err: %v\n", v, err)
continue
}
fmt.Printf("head %s succ, status: %v\n", v, resp.Status)
}
}

栗子（form）

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

const form = `
<html>
<body>
<form action="#" method="post" name="bar">
<input type="text" name="in"/>
<input type="text" name="in"/>
<input type="submit" value="Submit"/>
</form>
</body>
</html>
`

func SimpleServer(w http.ResponseWriter, request *http.Request) {
io.WriteString(w, "Hello World.")
}

func FormServer(w http.ResponseWriter, request *http.Request) {
w.Header().Set("Content-Type", "text/html")
switch request.Method {
case "GET":
io.WriteString(w, form)
case "POST":
request.ParseForm()
io.WriteString(w, request.Form["in"][1])
io.WriteString(w, "\n")
io.WriteString(w, request.FormValue("in"))
}
}

func logPanics(handle http.HandlerFunc) http.HandlerFunc {
return func(writer http.ResponseWriter, request *http.Request) {
defer func() {
if x := recover(); x != nil {
log.Printf("[%v] caught panic: %v", request.RemoteAddr, x)
}
}()
handle(writer, request)
}
}

func main() {
http.HandleFunc("/test1", SimpleServer)
http.HandleFunc("/test2", logPanics(FormServer))
err := http.ListenAndServe("0.0.0.0:6000", nil)
if err != nil {
fmt.Println("http listen failed.")
}
}

栗子（template）

package main

import (
"fmt"
"html/template"
"net/http"
)

type Person struct {
Title string
Name  string
Age   int
}

func SimpleServer(w http.ResponseWriter, request *http.Request) {
indexFailPath := "./index.html"
t, err := template.ParseFiles(indexFailPath)
if err != nil {
fmt.Println("parse file err:", err)
return
}
p := Person{Name: "Nick", Age: 18, Title: "Good."}
if err = t.Execute(w, p); err != nil {
fmt.Println("There was an error:", err.Error())
return
}
}

func main() {
http.HandleFunc("/test1", SimpleServer)
err := http.ListenAndServe("0.0.0.0:9000", nil)
if err != nil {
fmt.Println("http listen failed.")
}
}

<html>
<head>
<title>
{{.Title}}
</title>
</head>
<body>
<p>{{.Name}}</p>
{{if gt .Age 18}}
<p>MAN: {{.Name}}</p>
{{else}}
<p>Kid: {{.Name}}</p>
{{end}}
</body>
</html>

更多用法

not 非
{{if not .condition}} 
{{end}}


and 与
{{if and .condition1 .condition2}} 
{{end}}


or 或
{{if or .condition1 .condition2}} 
{{end}}


eq 等于
{{if eq .var1 .var2}} 
{{end}}


ne 不等于
{{if ne .var1 .var2}} 
{{end}}


lt 小于 (less than)
{{if lt .var1 .var2}} 
{{end}}


le 小于等于
{{if le .var1 .var2}} 
{{end}}


gt 大于
{{if gt .var1 .var2}} 
{{end}}


ge 大于等于
{{if ge .var1 .var2}} 
{{end}}

range 循环 {{range.}} {{end }}

Appendix

大端字节序的实现

data, err := json.Marshal("hello world")
if err != nil {
return
}

var buf [4]byte
packLen := uint32(len(data))
fmt.Println("packlen:", packLen)

// 前4个字节表示data大小
binary.BigEndian.PutUint32(buf[0:4], packLen)

n, err := conn.Write(buf[:])
if err != nil || n != 4 {
fmt.Println("write data  failed")
return
}

_, err = conn.Write([]byte(data))
if err != nil {
return
}

Http 状态码

const (
StatusContinue           = 100
StatusSwitchingProtocols = 101
StatusOK                   = 200
StatusCreated              = 201
StatusAccepted             = 202
StatusNonAuthoritativeInfo = 203
StatusNoContent            = 204
StatusResetContent         = 205
StatusPartialContent       = 206
StatusMultipleChoices   = 300
StatusMovedPermanently  = 301
StatusFound             = 302
StatusSeeOther          = 303
StatusNotModified       = 304
StatusUseProxy          = 305
StatusTemporaryRedirect = 307
StatusBadRequest                   = 400
StatusUnauthorized                 = 401
StatusPaymentRequired              = 402
StatusForbidden                    = 403
StatusNotFound                     = 404
StatusMethodNotAllowed             = 405
StatusNotAcceptable                = 406
StatusProxyAuthRequired            = 407
StatusRequestTimeout               = 408
StatusConflict                     = 409
StatusGone                         = 410
StatusLengthRequired               = 411
StatusPreconditionFailed           = 412
StatusRequestEntityTooLarge        = 413
StatusRequestURITooLong            = 414
StatusUnsupportedMediaType         = 415
StatusRequestedRangeNotSatisfiable = 416
StatusExpectationFailed            = 417
StatusTeapot                       = 418
StatusInternalServerError     = 500
StatusNotImplemented          = 501
StatusBadGateway              = 502
StatusServiceUnavailable      = 503
StatusGatewayTimeout          = 504
StatusHTTPVersionNotSupported = 505
)