上文只是解决了编码/解码问题，前提是收到的数据包没有产生粘包问题，解决粘包就是要正确分割字节流中的数据。一般有以下做法：
定长分隔(每个数据包最大为该长度) 缺点是数据不足时会浪费传输资源 特定字符分隔(如rn) 缺点是如果正文中有rn就会导致问题 在数据包中添加长度字段(本文采用的)golang提供了bufio.Scanner来解决粘包问题。
scanner := bufio.NewScanner(reader) // reader为实现了io.Reader接口的对象，如net.Conn
scanner.Split(func(data []byte, atEOF bool) (advance int, token []byte, err error) {
if !atEOF && data[0] == 'V' { // 由于我们定义的数据包头最开始为两个字节的版本号，所以只有以V开头的数据包才处理
if len(data) > 4 { // 如果收到的数据>4个字节(2字节版本号+2字节数据包长度)
length := int16(0)
binary.Read(bytes.NewReader(data[2:4]), binary.BigEndian, &length) // 读取数据包第3-4字节(int16)=>数据部分长度
if int(length)+4 <= len(data) { // 如果读取到的数据正文长度+2字节版本号+2字节数据长度不超过读到的数据(实际上就是成功完整的解析出了一个包)
return int(length) + 4, data[:int(length)+4], nil
}
}
}
return
})
// 打印接收到的数据包
for scanner.Scan() {
scannedPack := new(Package)
scannedPack.Unpack(bytes.NewReader(scanner.Bytes()))
log.Println(scannedPack)
}
本文的核心就在于scanner.Split方法，该方法用来解析TCP数据包
完整源码
package main
import (
"bufio"
"bytes"
"encoding/binary"
"fmt"
"io"
"log"
"os"
"time"
)
type Package struct {
Version [2]byte // 协议版本
Length int16 // 数据部分长度
Timestamp int64 // 时间戳
HostnameLength int16 // 主机名长度
Hostname []byte // 主机名
TagLength int16 // Tag长度
Tag []byte // Tag
Msg []byte // 数据部分长度
}
func (p *Package) Pack(writer io.Writer) error {
var err error
err = binary.Write(writer, binary.BigEndian, &p.Version)
err = binary.Write(writer, binary.BigEndian, &p.Length)
err = binary.Write(writer, binary.BigEndian, &p.Timestamp)
err = binary.Write(writer, binary.BigEndian, &p.HostnameLength)
err = binary.Write(writer, binary.BigEndian, &p.Hostname)
err = binary.Write(writer, binary.BigEndian, &p.TagLength)
err = binary.Write(writer, binary.BigEndian, &p.Tag)
err = binary.Write(writer, binary.BigEndian, &p.Msg)
return err
}
func (p *Package) Unpack(reader io.Reader) error {
var err error
err = binary.Read(reader, binary.BigEndian, &p.Version)
err = binary.Read(reader, binary.BigEndian, &p.Length)
err = binary.Read(reader, binary.BigEndian, &p.Timestamp)
err = binary.Read(reader, binary.BigEndian, &p.HostnameLength)
p.Hostname = make([]byte, p.HostnameLength)
err = binary.Read(reader, binary.BigEndian, &p.Hostname)
err = binary.Read(reader, binary.BigEndian, &p.TagLength)
p.Tag = make([]byte, p.TagLength)
err = binary.Read(reader, binary.BigEndian, &p.Tag)
p.Msg = make([]byte, p.Length-8-2-p.HostnameLength-2-p.TagLength)
err = binary.Read(reader, binary.BigEndian, &p.Msg)
return err
}
func (p *Package) String() string {
return fmt.Sprintf("version:%s length:%d timestamp:%d hostname:%s tag:%s msg:%s",
p.Version,
p.Length,
p.Timestamp,
p.Hostname,
p.Tag,
p.Msg,
)
}
func main() {
hostname, err := os.Hostname()
if err != nil {
log.Fatal(err)
}
pack := &Package{
Version: [2]byte{'V', '1'},
Timestamp: time.Now().Unix(),
HostnameLength: int16(len(hostname)),
Hostname: []byte(hostname),
TagLength: 4,
Tag: []byte("demo"),
Msg: []byte(("现在时间是:" + time.Now().Format("2006-01-02 15:04:05"))),
}
pack.Length = 8 + 2 + pack.HostnameLength + 2 + pack.TagLength + int16(len(pack.Msg))
buf := new(bytes.Buffer)
// 写入四次，模拟TCP粘包效果
pack.Pack(buf)
pack.Pack(buf)
pack.Pack(buf)
pack.Pack(buf)
// scanner
scanner := bufio.NewScanner(buf)
scanner.Split(func(data []byte, atEOF bool) (advance int, token []byte, err error) {
if !atEOF && data[0] == 'V' {
if len(data) > 4 {
length := int16(0)
binary.Read(bytes.NewReader(data[2:4]), binary.BigEndian, &length)
if int(length)+4 <= len(data) {
return int(length) + 4, data[:int(length)+4], nil
}
}
}
return
})
for scanner.Scan() {
scannedPack := new(Package)
scannedPack.Unpack(bytes.NewReader(scanner.Bytes()))
log.Println(scannedPack)
}
if err := scanner.Err(); err != nil {
log.Fatal("无效数据包")
}
}
