自定义协议（应用层协议）——网络版计算机基于TCP传输协议

应用层：自定义网络协议：序列化和反序列化，如果是TCP传输的：还要关心区分报文边界（在序列化设计的时候设计好）——粘包问题
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1、首先想要使用TCP协议传输的网络，服务器和客户端都应该要创建自己的套接字，因为两个都要创建，所以我们把套接字封装为一个类：
封装方法：设计模式：模版方法：先写一个模版类（基类），里面有各种函数，然后再写一个派生类里面有各种方法的实现，创建对象的时候

#pragma once
#include <iostream>
#include <string>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

#define Convert(addrptr) ((struct sockaddr *)addrptr)

namespace Net_Work
{
    const static int defaultsockfd = -1;
    const int backlog = 5;

    enum
    {
        SocketError = 1,
        BindError,
        ListenError,
    };

    // 封装一个基类，Socket接口类
    // 设计模式：模版方法类
    class Socket
    {
    public:
        virtual ~Socket() {}
        virtual void CreateSocketOrDie() = 0;
        virtual void BindSocketOrDie(uint16_t port) = 0;
        virtual void ListenSocketOrDie(int backlog) = 0;
        virtual Socket *AcceptConnection(std::string *peerip, uint16_t *peerport) = 0;
        virtual bool ConnectServer(std::string &serverip, uint16_t serverport) = 0;
        virtual int GetSockFd() = 0;
        virtual void SetSockFd(int sockfd) = 0;
        virtual void CloseSocket() = 0;
        virtual bool Recv(std::string *buffer, int size) = 0;
        // TODO
    public:
        // 创建服务器端的套接字，并设置为监听状态监听套接字
        void BuildListenSocketMethod(uint16_t port, int backlog)
        {
            CreateSocketOrDie();
            BindSocketOrDie(port);
            ListenSocketOrDie(backlog);
        }
        // 创建客户端的套接字，并且申请链接
        bool BuildConnectSocketMethod(std::string &serverip, uint16_t serverport)
        {
            CreateSocketOrDie();
            return ConnectServer(serverip, serverport);
        }

        void BuildNormalSocketMethod(int sockfd)
        {
            SetSockFd(sockfd);
        }
    };

    class TcpSocket : public Socket
    {
    public:
        TcpSocket(int sockfd = defaultsockfd) : _sockfd(sockfd)
        {
        }
        ~TcpSocket()
        {
        }
        void CreateSocketOrDie() override // 创建套接字
        {
            _sockfd = ::socket(AF_INET, SOCK_STREAM, 0);
            if (_sockfd < 0)
                exit(SocketError);
        }
        void BindSocketOrDie(uint16_t port) override // 绑定套接字
        {
            struct sockaddr_in local;
            memset(&local, 0, sizeof(local));
            local.sin_family = AF_INET;
            local.sin_addr.s_addr = INADDR_ANY;
            local.sin_port = htons(port);

            int n = ::bind(_sockfd, Convert(&local), sizeof(local));
            if (n < 0)
                exit(BindError);
        }
        void ListenSocketOrDie(int backlog) override // 设置套接字为监听状态
        {
            int n = ::listen(_sockfd, backlog);
            if (n < 0)
                exit(ListenError);
        }
        // 获取链接套接字——服务器
        Socket *AcceptConnection(std::string *peerip, uint16_t *peerport) override
        {
            struct sockaddr_in peer;
            socklen_t len = sizeof(peer);
            int newsockfd = ::accept(_sockfd, Convert(&peer), &len);
            if (newsockfd < 0)
                return nullptr;
            *peerport = ntohs(peer.sin_port);
            *peerip = inet_ntoa(peer.sin_addr);
            Socket *s = new TcpSocket(newsockfd);
            return s;
        }

        // 申请链接——客户端
        bool ConnectServer(std::string &serverip, uint16_t serverport) override
        {
            struct sockaddr_in server;
            memset(&server, 0, sizeof(server));
            server.sin_family = AF_INET;
            server.sin_addr.s_addr = inet_addr(serverip.c_str());
            server.sin_port = htons(serverport);

            int n = ::connect(_sockfd, Convert(&server), sizeof(server));
            if (n == 0)
                return true;
            else
                return false;
        }
        int GetSockFd() override
        {
            return _sockfd;
        }
        void SetSockFd(int sockfd) override
        {
            _sockfd = sockfd;
        }
        void CloseSocket() override
        {
            if (_sockfd > defaultsockfd)
                ::close(_sockfd);
        }
        bool Recv(std::string *buffer, int size)//接收消息到buffer中
        {
            char inbuffer[size];
            ssize_t n = recv(_sockfd, inbuffer, size - 1, 0);
            if (n > 0)
            {
                inbuffer[n] = 0;
                *buffer += inbuffer;
                return true;
            }
            else if (n == 0 || n < 0)
                return false;
        }

        private:
            int _sockfd;
        };
    }

创建服务器：
1、创建套接字
2、把套接字设置为监听状态
3、获取连接，产生新的套接字
4、把新的套接字作为新线程的参数传到新线程执行的代码中，实现收发消息的操作
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代码：

#pragma once

#include"Socket.hpp"
#include<pthread.h>
#include<functional>


using func_t=std::function<void(Net_Work::Socket* sockp)>;

//服务器类
class TcpServer;

class ThreadData
{
 public:
     ThreadData(TcpServer*tcp_this, Net_Work::Socket *sockp): _this(tcp_this), _sockp(sockp)
    {}
 public:
    TcpServer *_this;
    Net_Work::Socket *_sockp;
};

class TcpServer
{
    public:
    TcpServer(uint16_t port, func_t handler_request):_port(port),_listensocket(new Net_Work::TcpSocket()),_handler_request(handler_request)
    {
        _listensocket->BuildListenSocketMethod(_port,Net_Work::backlog);
    }

 static void *ThreadRun(void *args)
    {
        pthread_detach(pthread_self());//分离线程
        ThreadData *td=static_cast<ThreadData*>(args);
        td->_this->_handler_request(td->_sockp);
        td->_sockp->CloseSocket();
        delete td->_sockp;
        delete td;
        return nullptr;
    }
    void Loop()
    {
        while(true)
        {
            //获取连接
        std::string peerip;
        uint16_t peerport;
        Net_Work::Socket* newsock=_listensocket->AcceptConnection(&peerip,&peerport);
        if(newsock==nullptr) continue;;
        std::cout<<"获取了一个新链接,sockfd: "<<newsock->GetSockFd()<<"client info:"<< peerip<<":"<<peerport<<std::endl;

        //创建线程去完成此次sockfd收发
        pthread_t tid;
        ThreadData *td=new ThreadData(this,newsock);
        pthread_create(&tid,nullptr,ThreadRun,td);
        }
    }
    ~TcpServer()
    {
        delete _listensocket;
    }
    private:
    int _port;
    Net_Work::Socket *_listensocket;
public:
    func_t _handler_request;

};

客户端：
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2、TCP是向字节流（字符串）

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序列化、反序列化

自定义协议就是定义双方都认识的结构化字段，并且协议中有序列化和反序列化的实现
先定义一个协议（结构化字段）——双方都能看到
设计模式：工厂模式：
客户端发送的结构体+序列化函数+反序列化函数
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服务器反序列化的接收的结构体+反序列函数+序列化函数
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代码：

#pragma once

#include <iostream>
#include <memory>

namespace Protocol
{

    const std::string ProtSep = " ";

    const std::string LineBreakSep = "\n";

    // 封装为报文——序列化的一部分
    std::string Encode(const std::string &message) //"x op y"或者"_result _code"
    {
        std::string len = std::to_string(message.size());
        std::string package = len + LineBreakSep + message + LineBreakSep; //"len\n""x op y\n"
        return package;
    }

    // 解报——反序列化的一部分
    bool Decode(std::string &package, std::string *message) //"len\n""x op y\n"
    {
        // 除了解报，我们还要判断是否认正确

        auto pos = package.find(LineBreakSep);
        if (pos == std::string::npos)
            return false;
        std::string lens = package.substr(0, pos);
        int messagelen = std::stoi(lens);
        int total = lens.size() + messagelen + 2 * LineBreakSep.size();
        if (package.size() < total)
            return false;
        // 至少有一个完整报文
        *message = package.substr(pos + LineBreakSep.size(), messagelen);
        // 收到的报文可能是"len\n""x op y\n""len\n""x op y\n""len\n""x op y\n"
        // 所以我解报一个报文后，要删除这个报文，让后面的继续Dcode解报
        package.erase(0, total);
        return true;
    }

    class Requset
    {
    public:
        Requset() : _data_x(0), _data_y(0), _oper(0)
        {
        }
        Requset(int x, int y, int op) : _data_x(x), _data_y(y), _oper(op)
        {
        }
        ~Requset()
        {
        }
        void Debug()
        {
            std::cout << "_data_x:" << _data_x << std::endl;
            std::cout << "_data_y:" << _data_y << std::endl;
            std::cout << "_oper:" << _oper << std::endl;
        }
        void Inc()
        {
            _data_x++;
            _data_y++;
        }
        // 自定义序列化协议：结构体数据->字符串
        bool Serialize(std::string *out)
        {
            //"x op y"
            *out = std::to_string(_data_x) + ProtSep + _oper + ProtSep + std::to_string(_data_y);
            return true;
        }
        // 反序列化   :  字符串->结构体数据
        bool Deserialize(std::string &in) //"x op y"
        {
            auto left = in.find(ProtSep);
            if (left == std::string::npos)
                return false;
            auto right = in.rfind(ProtSep);
            if (right == std::string::npos)
                return false;

            //[)
            _data_x = std::stoi(in.substr(0, left));
            _data_y = std::stoi(in.substr(right + ProtSep.size()));
            std::string oper = in.substr(left + ProtSep.size(), right - (left + ProtSep.size()));

            if (oper.size() == 1)
                return false;
            _oper = oper[0];
            return true;
        }
        int Getx() { return _data_x; }
        int Gety() { return _data_y; }
        char GetOper() { return _oper; }

        //_data_x+_data_y
        // 报文的自描述
        //"len\n""x op y\n"
    private:
        int _data_x; // 第一个参数
        int _data_y; // 第二个参数
        char _oper;  //+ - * / %
    };

    class Response
    {
    public:
        Response(): _rseult(0), _code(0)
        {
        }
        Response(int result, int code) : _result(result), _code(code)
        {
        }
        // 自定义序列化协议：结构体数据->字符串
        bool Serialize(std::string *out)
        {
            //"_result  _code"
            *out = std::to_string(_result) + ProtSep + std::to_string(_code);
            return true;
        }
        // 反序列化：字符串->数据架构数据
        bool Deserialize(std::string &in) //"_result  _code"
        {
            auto pos = in.find(ProtSep);
            if (pos == std::string::npos)
                return false;
            _result = std::stoi(in.substr(0, pos));
            _code = std::stoi(in.substr(pos + ProtSep.size()));
            return true;
        }
        void SetResult(int res) { _result = res; }
        void SetCode(int code){ _code=code;}

    private:
        int _result; // 运算结果
        int _code;   // 运算状态
    };

    // 简单的工厂模式，建造类设计模式
    class Factory
    {
    public:
        std::shared_ptr<Requset> BulidRequest()
        {
            std::shared_ptr<Requset> req = std::make_shared<Requset>();
            return req;
        }
        std::shared_ptr<Requset> BulidRequest(int x, int y, int op)
        {
            std::shared_ptr<Requset> req = std::make_shared<Requset>(x, y, op);
            return req;
        }
        std::shared_ptr<Response> BulidResponse()
        {
            std::shared_ptr<Response> resp = std::make_shared<Response>();
            return resp;
        }
        std::shared_ptr<Response> BulidResponse(int result, int code)
        {
            std::shared_ptr<Response> resp = std::make_shared<Response>(result, code);
            return resp;
        }
    };
}