Protobuf简单使用及其抓包分析

早之前就用过Google的Protobuf做数据编码，一直没有深入理解其中的原理，最近做了一次通讯抓包，发现其中很多Protobuf编码的数据包，于是决定分析一下其中的数据包及其编码。

一、Protobuf的使用

首先来简单介绍一下Protobuf的使用，这里以windows下java开发为例，几个步骤：编写*.proto ->使用google提供的protoc.exe生成*.java->项目中导入protobuf的.jar包进行开发即可。先看这里的*.proto文件：

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package com;

message CMsg

{

required string msghead = 1;

required string msgbody = 2;

}

message CMsgHead

{

required int32 msglen = 1;

required int32 msgtype = 2;

required int32 msgseq = 3;

required int32 termversion = 4;

required int32 msgres = 5;

required string termid = 6;

}

message CMsgReg

{

optional int32 area = 1;

optional int32 region = 2;

optional int32 shop = 3;

optional int32 ret = 4;

optional string termid = 5;

}

使用protoc.exe生成java文件，命令如下：



将生成的Msg.java及protobuf-java-2.3.0.jar导入项目中进行开发，这里写一个服务器端ProtobufServer及客户端ProtobufClient

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package com;

import java.io.DataInputStream;

import java.io.DataOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.ServerSocket;

import java.net.Socket;

import com.Msg.CMsg;

import com.Msg.CMsgHead;

import com.Msg.CMsgReg;

public class ProtoServer implements Runnable {

@Override

public void run() {

try {

System.out.println("beign:");

ServerSocket serverSocket = new ServerSocket(12345);

while (true) {

System.out.println("等待接收用户连接：");

// 接受客户端请求

Socket client = serverSocket.accept();

DataOutputStream dataOutputStream;

DataInputStream dataInputStream;

try {

InputStream inputstream = client.getInputStream();

dataOutputStream = new DataOutputStream(

client.getOutputStream());

byte len[] = new byte[1024];

int count = inputstream.read(len);

byte[] temp = new byte[count];

for (int i = 0; i < count; i++) {

temp[i] = len[i];

}

CMsg msg = CMsg.parseFrom(temp);

CMsgHead head = CMsgHead.parseFrom(msg.getMsghead()

.getBytes());

System.out.println("==len===" + head.getMsglen());

System.out.println("==res===" + head.getMsgres());

System.out.println("==seq===" + head.getMsgseq());

System.out.println("==type===" + head.getMsgtype());

System.out.println("==Termid===" + head.getTermid());

System.out.println("==Termversion==="

+ head.getTermversion());

CMsgReg body = CMsgReg.parseFrom(msg.getMsgbody()

.getBytes());

System.out.println("==area==" + body.getArea());

System.out.println("==Region==" + body.getRegion());

System.out.println("==shop==" + body.getShop());

sendProtoBufBack(dataOutputStream);

inputstream.close();

} catch (Exception ex) {

System.out.println(ex.getMessage());

ex.printStackTrace();

} finally {

client.close();

System.out.println("close");

}

}

} catch (IOException e) {

System.out.println(e.getMessage());

}

}

private byte[] getProtoBufBack() {

// head

CMsgHead head = CMsgHead.newBuilder().setMsglen(10).setMsgtype(21)

.setMsgseq(32).setTermversion(43).setMsgres(54)

.setTermid("Server:head").build();

// body

CMsgReg body = CMsgReg.newBuilder().setArea(11).setRegion(22)

.setShop(33).setRet(44).setTermid("Server:body").build();

// Msg

CMsg msg = CMsg.newBuilder()

.setMsghead(head.toByteString().toStringUtf8())

.setMsgbody(body.toByteString().toStringUtf8()).build();

return msg.toByteArray();

}

private void sendProtoBufBack(DataOutputStream dataOutputStream) {

byte[] backBytes = getProtoBufBack();

// Integer len2 = backBytes.length;

// byte[] cmdHead2 = BytesUtil.IntToBytes4(len2);

try {

// dataOutputStream.write(cmdHead2, 0, cmdHead2.length);

dataOutputStream.write(backBytes, 0, backBytes.length);

dataOutputStream.flush();

} catch (IOException e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

Thread desktopServerThread = new Thread(new ProtoServer());

desktopServerThread.start();

}

}

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package com;

import java.io.InputStream;

import java.net.Socket;

import com.Msg.CMsg;

import com.Msg.CMsgHead;

import com.Msg.CMsgReg;

public class ProtoClient {

public static void main(String[] args) {

ProtoClient pc=new ProtoClient();

System.out.println("beign:");

pc.runget();

}

public void runget() {

Socket socket = null;

try {

//socket = new Socket("localhost", 12345);

socket = new Socket("192.168.85.152", 12345);

// head

CMsgHead head = CMsgHead.newBuilder().setMsglen(5).setMsgtype(1)

.setMsgseq(3).setTermversion(41).setMsgres(5)

.setTermid("Client:head").build();

// body

CMsgReg body = CMsgReg.newBuilder().setArea(11).setRegion(22)

.setShop(33).setRet(44).setTermid("Clent:body").build();

// Msg

CMsg msg = CMsg.newBuilder()

.setMsghead(head.toByteString().toStringUtf8())

.setMsgbody(body.toByteString().toStringUtf8()).build();

// 向服务器发送信息

System.out.println("sendMsg...");

msg.writeTo(socket.getOutputStream());

// 接受服务器的信息

InputStream input = socket.getInputStream();

System.out.println("recvMsg:");

byte[] by = recvMsg(input);

printMsg(CMsg.parseFrom(by));

input.close();

socket.close();

} catch (Exception e) {

System.out.println(e.toString());

}

}

public void printMsg(CMsg g) {

try {

CMsgHead h = CMsgHead.parseFrom(g.getMsghead().getBytes());

StringBuffer sb = new StringBuffer();

if (h.hasMsglen())

sb.append("==msglen===" + h.getMsglen() + "\n");

if (h.hasMsgres())

sb.append("==msgres===" + h.getMsgres() + "\n");

if (h.hasMsgseq())

sb.append("==msgseq===" + h.getMsgseq() + "\n");

if (h.hasMsgtype())

sb.append("==msgtype===" + h.getMsgtype() + "\n");

if (h.hasTermid())

sb.append("==termid===" + h.getTermid() + "\n");

if (h.hasTermversion())

sb.append("==termversion===" + h.getTermversion() + "\n");

CMsgReg bo = CMsgReg.parseFrom(g.getMsgbody().getBytes());

if (bo.hasArea())

sb.append("==area==" + bo.getArea() + "\n");

if (bo.hasRegion())

sb.append("==region==" + bo.getRegion() + "\n");

if (bo.hasShop())

sb.append("==shop==" + bo.getShop() + "\n");

if (bo.hasRet())

sb.append("==ret==" + bo.getRet() + "\n");

if (bo.hasTermid())

sb.append("==termid==" + bo.getTermid() + "\n");

System.out.println(sb.toString());

} catch (Exception e) {

e.printStackTrace();

}

}

public byte[] recvMsg(InputStream inpustream) {

byte[] temp = null;

try {

byte len[] = new byte[1024];

int count = inpustream.read(len);

temp = new byte[count];

for (int i = 0; i < count; i++) {

temp[i] = len[i];

}

return temp;

} catch (Exception e) {

System.out.println(e.toString());

return temp;

}

}

}

运行结果：

二、抓包分析

在上面socket通信过程中我使用了wireshark对其进行抓包，结果分析如下图



由上图我们可以很清楚的看到，protobuf编码其实类似tlv（tag length value）编码，其内部就是（tag, length, value)的组合，其中tag由(field_number<<3)|wire_type计算得出，field_number由我们在proto文件中定义，wire_type由protobuf根据proto中定义的字段类型决定，length长度采用一种叫做Varint 的数字表示方法，它是一种紧凑的表示数字的方法，用一个或多个字节来表示一个数字，值越小的数字使用越少的字节数，具体细节可以谷歌Varint。总之Protobuf
序列化后所生成的二进制消息非常紧凑，这得益于 Protobuf 采用了上面的 Encoding 方法。

参考文献：http://www.ibm.com/developerworks/cn/linux/l-cn-gpb/

源码下载：http://download.csdn.net/detail/wangqiuyun/8294015

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