NTP（Network Time Protocol，网络时间协议）是由RFC 1305定义的时间同步协议，用来在分布式时间服务器和客户端之间进行时间同步。NTP基于UDP报文进行传输，使用的UDP端口号为123。
使用NTP的目的是对网络内所有具有时钟的设备进行时钟同步，使网络内所有设备的时钟保持一致，从而使设备能够提供基于统一时间的多种应用。
对于运行NTP的本地系统，既可以接收来自其他时钟源的同步，又可以作为时钟源同步其他的时钟，并且可以和其他设备互相同步。
相信文本介绍看多也厌倦了，就不多废话，直接上干活
ntp.go
package main
import (
"bytes"
"encoding/binary"
)
const (
UNIX_STA_TIMESTAMP = 2208988800
)
/**
NTP协议 http://www.ntp.org/documentation.html
@author mengdj@outlook.com
*/
type Ntp struct {
//1:32bits
Li uint8 //2 bits
Vn uint8 //3 bits
Mode uint8 //3 bits
Stratum uint8
Poll uint8
Precision uint8
//2:
RootDelay int32
RootDispersion int32
ReferenceIdentifier int32
//64位时间戳
ReferenceTimestamp uint64 //指示系统时钟最后一次校准的时间
OriginateTimestamp uint64 //指示客户向服务器发起请求的时间
ReceiveTimestamp uint64 //指服务器收到客户请求的时间
TransmitTimestamp uint64 //指示服务器向客户发时间戳的时间
}
func NewNtp() (p *Ntp) {
//其他参数通常都是服务器返回的
p = &Ntp{Li: 0, Vn: 3, Mode: 3, Stratum: 0}
return p
}
/**
构建NTP协议信息
*/
func (this *Ntp) GetBytes() []byte {
//注意网络上使用的是大端字节排序
buf := &bytes.Buffer{}
head := (this.Li << 6) | (this.Vn << 3) | ((this.Mode << 5) >> 5)
binary.Write(buf, binary.BigEndian, uint8(head))
binary.Write(buf, binary.BigEndian, this.Stratum)
binary.Write(buf, binary.BigEndian, this.Poll)
binary.Write(buf, binary.BigEndian, this.Precision)
//写入其他字节数据
binary.Write(buf, binary.BigEndian, this.RootDelay)
binary.Write(buf, binary.BigEndian, this.RootDispersion)
binary.Write(buf, binary.BigEndian, this.ReferenceIdentifier)
binary.Write(buf, binary.BigEndian, this.ReferenceTimestamp)
binary.Write(buf, binary.BigEndian, this.OriginateTimestamp)
binary.Write(buf, binary.BigEndian, this.ReceiveTimestamp)
binary.Write(buf, binary.BigEndian, this.TransmitTimestamp)
//[27 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
return buf.Bytes()
}
func (this *Ntp) Parse(bf []byte, useUnixSec bool) {
var (
bit8 uint8
bit32 int32
bit64 uint64
rb *bytes.Reader
)
//貌似这binary.Read只能顺序读，不能跳着读，想要跳着读只能使用切片bf
rb = bytes.NewReader(bf)
binary.Read(rb, binary.BigEndian, &bit8)
//向右偏移6位得到前两位LI即可
this.Li = bit8 >> 6
//向右偏移2位,向右偏移5位,得到前中间3位
this.Vn = (bit8 << 2) >> 5
//向左偏移5位，然后右偏移5位得到最后3位
this.Mode = (bit8 << 5) >> 5
binary.Read(rb, binary.BigEndian, &bit8)
this.Stratum = bit8
binary.Read(rb, binary.BigEndian, &bit8)
this.Poll = bit8
binary.Read(rb, binary.BigEndian, &bit8)
this.Precision = bit8
//32bits
binary.Read(rb, binary.BigEndian, &bit32)
this.RootDelay = bit32
binary.Read(rb, binary.BigEndian, &bit32)
this.RootDispersion = bit32
binary.Read(rb, binary.BigEndian, &bit32)
this.ReferenceIdentifier = bit32
//以下几个字段都是64位时间戳(NTP都是64位的时间戳)
binary.Read(rb, binary.BigEndian, &bit64)
this.ReferenceTimestamp = bit64
binary.Read(rb, binary.BigEndian, &bit64)
this.OriginateTimestamp = bit64
binary.Read(rb, binary.BigEndian, &bit64)
this.ReceiveTimestamp = bit64
binary.Read(rb, binary.BigEndian, &bit64)
this.TransmitTimestamp = bit64
//转换为unix时间戳,先左偏移32位拿到64位时间戳的整数部分，然后ntp的起始时间戳 1900年1月1日 0时0分0秒 2208988800
if useUnixSec {
this.ReferenceTimestamp = (this.ReceiveTimestamp >> 32) - UNIX_STA_TIMESTAMP
if this.OriginateTimestamp > 0 {
this.OriginateTimestamp = (this.OriginateTimestamp >> 32) - UNIX_STA_TIMESTAMP
}
this.ReceiveTimestamp = (this.ReceiveTimestamp >> 32) - UNIX_STA_TIMESTAMP
this.TransmitTimestamp = (this.TransmitTimestamp >> 32) - UNIX_STA_TIMESTAMP
}
}
main.go
package main
import (
"fmt"
"log"
"net"
)
func main() {
var (
ntp *Ntp
buffer []byte
err error
ret int
)
//链接阿里云NTP服务器,NTP有很多免费服务器可以使用time.windows.com
conn, err := net.Dial("udp", "ntp1.aliyun.com:123")
defer func() {
if err := recover(); err != nil {
log.Println(err)
}
conn.Close()
}()
ntp = NewNtp()
conn.Write(ntp.GetBytes())
buffer = make([]byte, 2048)
ret, err = conn.Read(buffer)
if err == nil {
if ret > 0 {
ntp.Parse(buffer, true)
fmt.Println(fmt.Sprintf(
"LI:%d
版本:%d
模式:%d
精度:%d
轮询:%d
系统精度:%d
延时:%ds
最大误差:%d
时钟表示:%d
时间戳:%d %d %d %d
",
ntp.Li,
ntp.Vn,
ntp.Mode,
ntp.Stratum,
ntp.Poll,
ntp.Precision,
ntp.RootDelay,
ntp.RootDispersion,
ntp.ReferenceIdentifier,
ntp.ReferenceTimestamp,
ntp.OriginateTimestamp,
ntp.ReceiveTimestamp,
ntp.TransmitTimestamp,
))
}
}
}