1.自定義協議

開發者根據特定應用場景的需要，自行設計和制定的通信規則和數據格式??

? ?1.1 核心組成部分

一個典型的自定義協議通常包含以下幾個關鍵部分：

1. ?幀/報文格式 (Frame/Packet Format)??：定義了數據是如何打包的。這通常包括：

   • ?魔數 (Magic Number)??：一個特殊的標識符，用于快速識別數據包的開始或驗證協議類型。
   • ?包頭 (Header)??：包含元數據，如版本號、數據包類型、包體長度、序列號等。
   • ?包體 (Body/Payload)??：實際要傳輸的有效數據。
   • ?校驗和 (Checksum)??：用于檢驗數據在傳輸過程中是否出錯（如 CRC32）

? ?1.2?有關網絡計算器的自定義協議

#pragma once
#include<iostream>
#include"Socket.hpp"
#include<string>
#include<memory>
#include<jsoncpp/json/json.h>
#include<functional>
using namespace std;class Request     //請求
{
public:Request(){}Request(int x, int y, char oper): _x(x), _y(y), _oper(oper){}std::string Serialize()      //實現序列化{Json::Value root;root["x"] = _x;root["y"] = _y;root["oper"] = _oper;Json::FastWriter writer;return writer.write(root);}bool Deserialize(std::string &in)      //實現反序列化{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   //應答
{
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";    //報文的分隔符using func_t = std::function<Response(Request &req)>;       //func_t為自定義類型class Protocol
{
public:Protocol() {}Protocol(func_t func){}string encode(string &in)    //封裝報文{int len =in.size();string out = std::to_string(len) + sep + in+ sep;return out;}bool decode(string &buffer,string& package)    //解析報文（首先得判斷收到的報文是否完整）{auto pos = buffer.find(sep);if(pos == string::npos){return false;}string len_str = buffer.substr(0,pos);  //len_str為長度字段的字符串表示int len = atoi(len_str.c_str());        //數據部分的字節大小int tatoal_len = len_str.size() + len +2*sep.size();  //len_str.size()長度字段字符串的字節大小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)    //獲取請求{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)   //獲取應答{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)   //封裝請求的報文{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發生在應用層

? ? ?序列化和反序列化的核心作用是解決數據在【內存中的對象】與【可傳輸/存儲的格式】之間相互轉換的問題，簡要來說就是方便數據的傳輸，在上面的自定義協議中就運用了序列化和反序列化

? ? ? ??為了方便實現序列化和反序列化，我們可以用Jsoncpp（用于處理JSON數據的C++庫）

? ? ? 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
工廠
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\":\"張三\",
\"age\":30, \"city\":\"北京\"}";
// 解析 JSON 字符串
Json::Reader reader;
Json::Value root;
// 從字符串中讀取 JSON 數據
bool parsingSuccessful = reader.parse(json_string,
root);
if (!parsingSuccessful) {
// 解析失敗，輸出錯誤信息
std::cout << "Failed to parse JSON: " <<
reader.getFormattedErrorMessages() << std::endl;
return 1;
}
// 訪問 JSON 數據
std::string name = root["name"].asString();
int age = root["age"].asInt();
std::string city = root["city"].asString();
// 輸出結果
std::cout << "Name: " << name << std::endl;
std::cout << "Age: " << age << std::endl;
std::cout << "City: " << city << std::endl;
return 0;
}