Go语言学习笔记（六）net

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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, )
        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, )
    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": {""}})

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:     * time.Second,
    WriteTimeout:    * time.Second,
    MaxHeaderBytes:  << ,
}
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 *
        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"][])
        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: , 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 }}
            <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 []byte
    packLen := uint32(len(data))
    fmt.Println("packlen:", packLen)

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

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

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

Http  状态码

const (
    StatusContinue           =
    StatusSwitchingProtocols =
    StatusOK                   =
    StatusCreated              =
    StatusAccepted             =
    StatusNonAuthoritativeInfo =
    StatusNoContent            =
    StatusResetContent         =
    StatusPartialContent       =
    StatusMultipleChoices   =
    StatusMovedPermanently  =
    StatusFound             =
    StatusSeeOther          =
    StatusNotModified       =
    StatusUseProxy          =
    StatusTemporaryRedirect =
    StatusBadRequest                   =
    StatusUnauthorized                 =
    StatusPaymentRequired              =
    StatusForbidden                    =
    StatusNotFound                     =
    StatusMethodNotAllowed             =
    StatusNotAcceptable                =
    StatusProxyAuthRequired            =
    StatusRequestTimeout               =
    StatusConflict                     =
    StatusGone                         =
    StatusLengthRequired               =
    StatusPreconditionFailed           =
    StatusRequestEntityTooLarge        =
    StatusRequestURITooLong            =
    StatusUnsupportedMediaType         =
    StatusRequestedRangeNotSatisfiable =
    StatusExpectationFailed            =
    StatusTeapot                       =
    StatusInternalServerError     =
    StatusNotImplemented          =
    StatusBadGateway              =
    StatusServiceUnavailable      =
    StatusGatewayTimeout          =
    StatusHTTPVersionNotSupported =
)