1.自定义协议

开发者根据特定应用场景的需要，自行设计和制定的通信规则和数据格式  

   1.1 核心组成部分

一个典型的自定义协议通常包含以下几个关键部分：

1. ​帧/报文格式 (Frame/Packet Format)​​：定义了数据是如何打包的。这通常包括：

   • ​魔数 (Magic Number)​​：一个特殊的标识符，用于快速识别数据包的开始或验证协议类型。
   • ​包头 (Header)​​：包含元数据，如版本号、数据包类型、包体长度、序列号等。
   • ​包体 (Body/Payload)​​：实际要传输的有效数据。
   • ​校验和 (Checksum)​​：用于检验数据在传输过程中是否出错（如 CRC32）

   1.2 有关网络计算器的自定义协议

#pragma once
#include<iostream>
#include"Socket.hpp"
#include<string>
#include<memory>
#include<jsoncpp/json/json.h>
#include<functional>
using namespace std;class Request     //请求
{
public:Request(){}Request(int x, int y, char oper): _x(x), _y(y), _oper(oper){}std::string Serialize()      //实现序列化{Json::Value root;root["x"] = _x;root["y"] = _y;root["oper"] = _oper;Json::FastWriter writer;return writer.write(root);}bool Deserialize(std::string &in)      //实现反序列化{Json::Value root;Json::Reader reader;bool ok = reader.parse(in,root);if(!ok){return false;}_x = root["x"].asInt();_y = root["y"].asInt();_oper = root["oper"].asInt();}~Request(){}int X() { return _x; }int Y() { return _y; }char Oper() { return _oper; }
private:int _x;int _y;char _oper;};class Response   //应答
{
public:Response(){};Response(int result,int code):_result(result),_code(code){}std::string Serialize()    //序列化{Json::Value root;root["result"] = _result;root["code"] = _code;Json::FastWriter writer;return writer.write(root);}bool Deserialize(std::string &in)      //反序列化{Json::Value root;Json::Reader reader;bool ok = reader.parse(in,root);if(!ok){return false;}_result = root["result"].asInt();_code = root["code"].asInt();return true;}~Response(){};int setResult() { return _result; }int setCode() { return _code; }
private:int _result;int _code;};
const std::string sep = "\r\n";    //报文的分隔符using func_t = std::function<Response(Request &req)>;       //func_t为自定义类型class Protocol
{
public:Protocol() {}Protocol(func_t func){}string encode(string &in)    //封装报文{int len =in.size();string out = std::to_string(len) + sep + in+ sep;return out;}bool decode(string &buffer,string& package)    //解析报文（首先得判断收到的报文是否完整）{auto pos = buffer.find(sep);if(pos == string::npos){return false;}string len_str = buffer.substr(0,pos);  //len_str为长度字段的字符串表示int len = atoi(len_str.c_str());        //数据部分的字节大小int tatoal_len = len_str.size() + len +2*sep.size();  //len_str.size()长度字段字符串的字节大小if(buffer.size() < tatoal_len){return false;}package = buffer.substr(pos+sep.size(),len);buffer.erase(0,tatoal_len);return true;}void GetRequest(std::shared_ptr<Socket> &sock, InetAddr &client)    //获取请求{string buffer_queue;while(true){int n = socket->Recv(&buffer_queue);if(n>0){std::cout << "-----------request_buffer--------------" << std::endl;std::cout << buffer_queue << std::endl;std::cout << "------------------------------------" << std::endl;while(decode(buffer_queue,&package)){Request req;bool ret = req.Deserialize(package);if(!ret){std::cout << "Deserialize failed" << std::endl;continue;}Response rsp = _func(req);string rsp_str = rsp.Serialize();string out = encode(rsp_str);socket->Send(out);}}else if(n == 0){std::cout << "client quit" << std::endl;socket->Close();break;}else{if(errno == EAGAIN || errno == EWOULDBLOCK){std::cout << "data over" << std::endl;break;}std::cout << "recv error" << std::endl;socket->Close();break;}}}void Getresponse(std::shared_ptr<Socket> &sock)   //获取应答{string buffer_queue;while(true){int n = socket->Recv(&buffer_queue);if(n>0){std::cout << "-----------response_buffer--------------" << std::endl;std::cout << buffer_queue << std::endl;std::cout << "------------------------------------" << std::endl;while(decode(buffer_queue,&package)){Response rsp;bool ret = rsp.Deserialize(package);if(!ret){std::cout << "Deserialize failed" << std::endl;continue;}std::cout << "result: " << rsp.setResult() << " code: " << rsp.setCode() << std::endl;}}else if(n == 0){std::cout << "server quit" << std::endl;socket->Close();break;}else{if(errno == EAGAIN || errno == EWOULDBLOCK){std::cout << "data over" << std::endl;break;}std::cout << "recv error" << std::endl;socket->Close();break;}}}string BuildRequest(int x, int y, char oper)   //封装请求的报文{Request req(x,y,oper);string req_str = req.Serialize();string out = encode(req_str);return out;}~Protocol() {}
private:func_t _func;std::shared_ptr<Socket> socket;string package;string buffer_queue;};

2.序列化和反序列化

     序列化和反序列化都是发生在应用层

     序列化和反序列化的核心作用是解决数据在【内存中的对象】与【可传输/存储的格式】之间相互转换的问题，简要来说就是方便数据的传输，在上面的自定义协议中就运用了序列化和反序列化

        为了方便实现序列化和反序列化，我们可以用Jsoncpp（用于处理JSON数据的C++库）

      2.1 序列化

#include <iostream>
#include <string>
#include <jsoncpp/json/json.h>
int main()
{
Json::Value root;
root["name"] = "joe";
root["sex"] = "男";
std::string s = root.toStyledString();
std::cout << s << std::endl;
return 0;
}
$ ./test.exe
{
"name" : "joe",
"sex" : "男"
}

#include <iostream>
#include <string>
#include <sstream>
#include <memory>
#include <jsoncpp/json/json.h>
int main()
{
Json::Value root;
root["name"] = "joe";
root["sex"] = "男";
Json::StreamWriterBuilder wbuilder; // StreamWriter 的
工厂
std::unique_ptr<Json::StreamWriter>
writer(wbuilder.newStreamWriter());
std::stringstream ss;
writer->write(root, &ss);
std::cout << ss.str() << std::endl;
return 0;
}
$ ./test.exe
{
"name" : "joe",
"sex" : "男"
}

#include <sstream>
#include<iostream>
#include<string>
#include <memory>
#include <jsoncpp/json/json.h>
int main()
{
Json::Value root;
root["name"] = "joe";
root["sex"] = "男";
Json::FastWriter writer;
std::string s = writer.write(root);
std::cout << s << std::endl;
return 0;
}
$ ./test.exe
{"name":"joe","sex":"男"}
#include <iostream>
#include <string>
#include <sstream>
#include <memory>
#include <jsoncpp/json/json.h>
int main()
{
Json::Value root;
root["name"] = "joe";
root["sex"] = "男";
// Json::FastWriter writer;
Json::StyledWriter writer;
std::string s = writer.write(root);
std::cout << s << std::endl;
return 0;
}

2.2 反序列化

#include <iostream>
#include <string>
#include <jsoncpp/json/json.h>
int main() {
// JSON 字符串
std::string json_string = "{\"name\":\"张三\",
\"age\":30, \"city\":\"北京\"}";
// 解析 JSON 字符串
Json::Reader reader;
Json::Value root;
// 从字符串中读取 JSON 数据
bool parsingSuccessful = reader.parse(json_string,
root);
if (!parsingSuccessful) {
// 解析失败，输出错误信息
std::cout << "Failed to parse JSON: " <<
reader.getFormattedErrorMessages() << std::endl;
return 1;
}
// 访问 JSON 数据
std::string name = root["name"].asString();
int age = root["age"].asInt();
std::string city = root["city"].asString();
// 输出结果
std::cout << "Name: " << name << std::endl;
std::cout << "Age: " << age << std::endl;
std::cout << "City: " << city << std::endl;
return 0;
}