go smtp示例

​书接上文邮件实现详解，这里我们及我们简单复习一下smtp的指令如下：

telnet smtp.163.com 25
[outpout]
ehlo dz45693
[outpout]
auth login
[outpout]
输入用户名base64
[outpout]
输入密码base64
mail from:<dz45693@163.com>
[outpout]
rcpt to:<dz45693@sina.com>
[outpout]
data
[outpout]
from:<dz45693@163.com>
to:<dz45693@sina.com>
subject:hello world
 
This is the first email sent by hand using the SMTP protocol
.
quit　　

​

好，那我们下现在用go实现代码让如下： 这里只是一个demo，主要熟悉smtp命令

package main

import (
    "bufio"
    "encoding/base64"
    "fmt"
    "net"
    "strconv"
    "strings"
)


func main() {
    testSmtp()
}

var gConn net.Conn
var gRead *bufio.Reader
var gWrite *bufio.Writer

//可以放到这样的类里
type TcpClient struct {
    Conn  net.Conn
    Read  *bufio.Reader
    Write *bufio.Writer
} //

func Connect(host string, port int) (net.Conn, *bufio.Reader, *bufio.Writer) {
    addr := host + ":" + strconv.Itoa(port)
    conn, err := net.Dial("tcp", addr)
    if err != nil {
        return nil, nil, nil
    }

    reader := bufio.NewReader(conn)
    writer := bufio.NewWriter(conn)

    return conn, reader, writer
} //

//收取一行,可再优化
func RecvLine() string {
    line, err := gRead.ReadString('\n') //如何设定超时?
    if err != nil {
        fmt.Print(err)
        return ""
    }

    line = strings.Split(line, "\r")[0] //还要再去掉 "\r"，其实不去掉也可以
    return line
}

func SendLine(line string) {
    gWrite.WriteString(line + "\r\n")
    gWrite.Flush()
}

//解码一行命令,这里比较简单就是按空格进行分隔就行了
func DecodeCmd(line string, sp string) []string {
    tmp := strings.Split(line, sp)
    var cmds = []string{"", "", "", "", ""} //先定义多几个，以面后面使用时产生异常
    for i := 0; i < len(tmp); i++ {
        if i >= len(cmds) {
            break
        }
        cmds[i] = tmp[i]
    }
    return cmds
}

//读取多行结果
func RecvMCmd() string {
    i := 0
    rs := ""
    mLine := ""
    for i = 0; i < 50; i++ {
        rs = RecvLine() //只收取一行
        mLine = mLine + rs + "\r\n"
        if len(rs) < 4 {
            break
        } //长度要足够
        c4 := rs[4-1] //第4个字符
        if ' ' == c4 {
            break
        } //第4个字符是空格就表示读取完了//也可以判断 "250[空格]"
    }
    return mLine
}

//简单的测试一下 smtp
func testSmtp() {
    //连接
    gConn, gRead, gWrite = Connect("smtp.163.com", 25)
    defer gConn.Close()
    //收取一行
    line := RecvLine()
    fmt.Println("recv:" + line)

    //解码一下,这样后面的 EHLO 才能有正确的第二个参数
    cmds := DecodeCmd(line, " ")
    domain := cmds[1] //要从对方的应答中取出域名//空格分开的各个命令参数中的第二个

    //发送一个命令
    SendLine("EHLO" + " " + domain) //domain 要求其实来自 HELO 命令//HELO <SP> <domain> <CRLF>

    //收取多行
    line = RecvMCmd()
    fmt.Println("recv:" + line)

    //--------------------------------------------------
    //用 base64 登录
    SendLine("AUTH LOGIN")

    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    s := "dz45693" //要换成你的用户名,注意 163 邮箱的话不要带后面的 @域名 部分
    s = base64.StdEncoding.EncodeToString([]byte(s))
    SendLine(s)

    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    s = "xxxxx" //要换成您的密码
    s = base64.StdEncoding.EncodeToString([]byte(s))
    SendLine(s)

    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    //--------------------------------------------------
    //邮件内容
    from := "dz45693@163.com"
    to := "dz45693@sina.com"

    SendLine("MAIL FROM: <" + from + ">") //注意"<" 符号和前面的空格。空格在协议中有和没有都可能，最好还是有
    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    SendLine("RCPT TO: <" + to + ">")
    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    SendLine("DATA")
    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

//发送邮件头
    SendLine("from:<dz45693@163.com>")
    SendLine("to:<dz45693@sina.com>")
    SendLine("subject:hello world")
    SendLine("") //发送空行 后面就是邮件体
    SendLine("This is the first email sent by hand using the SMTP protocol")

    SendLine(".") //邮件结束符

    //收取一行
    line = RecvLine()
    fmt.Println("recv:" + line)

    SendLine("quit") //链接推出
    line = RecvLine()
    fmt.Println("recv:" + line)
} //

运行结果图下：

 在go的sdk中提供了SendMail方法【发送邮件后这个方法会关闭链接】，实现如下：

实现如下：

func SendMailBySmtp(){
    auth := smtp.PlainAuth("", "dz45693@163.com", "xxx", "smtp.163.com")
    to := []string{"dz45693@sina.com"}
    image,_:=ioutil.ReadFile("d:\\Downloads\\1.png")
    imageBase64:=base64.StdEncoding.EncodeToString(image)
    msg := []byte("from:dz45693@163.com\r\n"+
        "to: dz45693@sina.com\r\n" +
        "Subject: hello,subject!\r\n"+
        "Content-Type:multipart/mixed;boundary=a\r\n"+
        "Mime-Version:1.0\r\n"+
        "\r\n" +
        "--a\r\n"+
        "Content-type:text/plain;charset=utf-8\r\n"+
        "Content-Transfer-Encoding:quoted-printable\r\n"+
        "\r\n"+
        "此处为正文内容!\r\n"+
        "--a\r\n"+
        "Content-type:image/jpg;name=1.jpg\r\n"+
        "Content-Transfer-Encoding:base64\r\n"+
        "\r\n"+
        imageBase64+"\r\n"+
        "--a--\r\n")
    err := smtp.SendMail("smtp.163.com:25", auth, "dz45693@163.com", to, msg)
    if err != nil {
        fmt.Println(err)
    }
}

运行效果

 示例如下：

func SendMailByGomailOne(){
    m := gomail.NewMessage()
    m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
    m.SetHeader("To", "dz45693@sina.com")
    m.SetHeader("Subject", "hello SendMailByGomailOne!")
    m.Embed("d:\\Downloads\\1.png")
    m.SetBody("text/html", "此处为正文121333!")

    d := gomail.NewDialer("smtp.163.com", 25, "dz45693@163.com", "xxxx#")

    if err := d.DialAndSend(m); err != nil {
        panic(err)
    }
}

运行结果：

来我们看看DialAndSend的实现如下： 

package gomail

import (
    "crypto/tls"
    "fmt"
    "io"
    "net"
    "net/smtp"
    "strings"
    "time"
)

// A Dialer is a dialer to an SMTP server.
type Dialer struct {
    // Host represents the host of the SMTP server.
    Host string
    // Port represents the port of the SMTP server.
    Port int
    // Username is the username to use to authenticate to the SMTP server.
    Username string
    // Password is the password to use to authenticate to the SMTP server.
    Password string
    // Auth represents the authentication mechanism used to authenticate to the
    // SMTP server.
    Auth smtp.Auth
    // SSL defines whether an SSL connection is used. It should be false in
    // most cases since the authentication mechanism should use the STARTTLS
    // extension instead.
    SSL bool
    // TSLConfig represents the TLS configuration used for the TLS (when the
    // STARTTLS extension is used) or SSL connection.
    TLSConfig *tls.Config
    // LocalName is the hostname sent to the SMTP server with the HELO command.
    // By default, "localhost" is sent.
    LocalName string
}

// NewDialer returns a new SMTP Dialer. The given parameters are used to connect
// to the SMTP server.
func NewDialer(host string, port int, username, password string) *Dialer {
    return &Dialer{
        Host:     host,
        Port:     port,
        Username: username,
        Password: password,
        SSL:      port == 465,
    }
}

// NewPlainDialer returns a new SMTP Dialer. The given parameters are used to
// connect to the SMTP server.
//
// Deprecated: Use NewDialer instead.
func NewPlainDialer(host string, port int, username, password string) *Dialer {
    return NewDialer(host, port, username, password)
}

// Dial dials and authenticates to an SMTP server. The returned SendCloser
// should be closed when done using it.
func (d *Dialer) Dial() (SendCloser, error) {
    conn, err := netDialTimeout("tcp", addr(d.Host, d.Port), 10*time.Second)
    if err != nil {
        return nil, err
    }

    if d.SSL {
        conn = tlsClient(conn, d.tlsConfig())
    }

    c, err := smtpNewClient(conn, d.Host)
    if err != nil {
        return nil, err
    }

    if d.LocalName != "" {
        if err := c.Hello(d.LocalName); err != nil {
            return nil, err
        }
    }

    if !d.SSL {
        if ok, _ := c.Extension("STARTTLS"); ok {
            if err := c.StartTLS(d.tlsConfig()); err != nil {
                c.Close()
                return nil, err
            }
        }
    }

    if d.Auth == nil && d.Username != "" {
        if ok, auths := c.Extension("AUTH"); ok {
            if strings.Contains(auths, "CRAM-MD5") {
                d.Auth = smtp.CRAMMD5Auth(d.Username, d.Password)
            } else if strings.Contains(auths, "LOGIN") &&
                !strings.Contains(auths, "PLAIN") {
                d.Auth = &loginAuth{
                    username: d.Username,
                    password: d.Password,
                    host:     d.Host,
                }
            } else {
                d.Auth = smtp.PlainAuth("", d.Username, d.Password, d.Host)
            }
        }
    }

    if d.Auth != nil {
        if err = c.Auth(d.Auth); err != nil {
            c.Close()
            return nil, err
        }
    }

    return &smtpSender{c, d}, nil
}

func (d *Dialer) tlsConfig() *tls.Config {
    if d.TLSConfig == nil {
        return &tls.Config{ServerName: d.Host}
    }
    return d.TLSConfig
}

func addr(host string, port int) string {
    return fmt.Sprintf("%s:%d", host, port)
}

// DialAndSend opens a connection to the SMTP server, sends the given emails and
// closes the connection.
func (d *Dialer) DialAndSend(m ...*Message) error {
    s, err := d.Dial()
    if err != nil {
        return err
    }
    defer s.Close()

    return Send(s, m...)
}

type smtpSender struct {
    smtpClient
    d *Dialer
}

func (c *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
    if err := c.Mail(from); err != nil {
        if err == io.EOF {
            // This is probably due to a timeout, so reconnect and try again.
            sc, derr := c.d.Dial()
            if derr == nil {
                if s, ok := sc.(*smtpSender); ok {
                    *c = *s
                    return c.Send(from, to, msg)
                }
            }
        }
        return err
    }

    for _, addr := range to {
        if err := c.Rcpt(addr); err != nil {
            return err
        }
    }

    w, err := c.Data()
    if err != nil {
        return err
    }

    if _, err = msg.WriteTo(w); err != nil {
        w.Close()
        return err
    }

    return w.Close()
}

func (c *smtpSender) Close() error {
    return c.Quit()
}

// Stubbed out for tests.
var (
    netDialTimeout = net.DialTimeout
    tlsClient      = tls.Client
    smtpNewClient  = func(conn net.Conn, host string) (smtpClient, error) {
        return smtp.NewClient(conn, host)
    }
)

type smtpClient interface {
    Hello(string) error
    Extension(string) (bool, string)
    StartTLS(*tls.Config) error
    Auth(smtp.Auth) error
    Mail(string) error
    Rcpt(string) error
    Data() (io.WriteCloser, error)
    Quit() error
    Close() error
}

 DialAndSend ,首先调用Dial方法创建连接，然后发送邮件，最后关闭链接，如果要频繁发邮件，那么是否保持长连接更好了？这里的Dial 调用了smtp.NewClient 创建smtp.Client对象c,然后调用c.Hello ,c.Auth，send 实际是调用c.Mail,c.Rcpt,c.Data，那么我们可以自己调用Dial方法 然后循环调用send方法，最后在close。

代码如下：

func SendMailByGomailTwo() {
    d := gomail.NewDialer("smtp.163.com", 25, "dz45693@163.com", "xxx")
    m := gomail.NewMessage()
    m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
    m.SetHeader("To", "dz45693@sina.com")
    m.SetHeader("Subject", "hello SendMailByGomailtwo!")
    m.Embed("d:\\Downloads\\1.png")
    m.SetBody("text/html", "此处为正文121333!SendMailByGomailtwo")

    s, err := d.Dial()
    if err != nil {
        panic(err)
    }
    defer s.Close()

    err = gomail.Send(s, m)
    if err != nil {
        panic(err)
    }

    m.Reset()
    m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
    m.SetHeader("To", "dz45693@sina.com")
    m.SetHeader("Subject", "hello SendMailByGomailthree!")
    m.Embed("d:\\Downloads\\2.png")
    m.SetBody("text/html", "此处为正文1SendMailByGomailthreeSendMailByGomailthree!")
    err = gomail.Send(s, m)
    if err != nil {
        panic(err)
    }
}

运行结果：