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0. 前言

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本文中用到的Log.hpp在笔者的历史文章中都有涉及，这里就不再粘贴源码了，学习地址如下：https://blog.csdn.net/weixin_73870552/article/details/145434855?spm=1001.2014.3001.5501。

TCP相对于UDP更加复杂，这里只介绍TCP的封装，学习完后，大家可以自己尝试UDP的封装。

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1. Socket.hpp

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采用模版方法类的设计模式，基类方法由子类实现

#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)

// 错误码
enum {
    SocketError = 1,
    BindError,
    ListenError
};

const static int defaultsockfd = -1;
const int backlog = 5;      // 这个参数后面讲

// 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;               // 创建套接字
    virtual void BindSocketOrDie(uint16_t port) = 0;    // 绑定
    virtual void ListenSocketOrDie(int backlog) = 0;    // 监听
    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;
    virtual void Send(std::string &send_str) = 0;
public:
    void BuildListenSocketMethod(uint16_t port, int backlog)
    {
        CreateSocketOrDie();
        BindSocketOrDie(port);
        ListenSocketOrDie(backlog);
    }

    bool BuildConnectSocketMethod(std::string &serverip, uint16_t serverport)
    {
        CreateSocketOrDie();
        return ConnectServer(serverip, serverport);
    }

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

// TCP
class TcpSocket : public Socket
{
public:
    TcpSocket(int sockfd = defaultsockfd)
        : _sockfd(sockfd)
    {}

    ~TcpSocket()
    {}

    void CreateSocketOrDie() override
    {
        _sockfd = ::socket(AF_INET, SOCK_STREAM, 0);
        if(_sockfd < 0) exit(SocketError);
    }

    void BindSocketOrDie(uint16_t port) override
    {
        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
    {
        int n = ::listen(_sockfd, backlog);
        if(n < 0) exit(ListenError);
    }

    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;
        *peerip = inet_ntoa(peer.sin_addr);
        *peerport = ntohs(peer.sin_port);
        Socket *s = new TcpSocket(newsockfd);
        return s;
    }

    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) override
    {
        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) return false;
        else return false;
    }

    void Send(std::string &send_str) override
    {
        // 这一块涉及到多路转接，我们之后统一说
        send(_sockfd, send_str.c_str(), send_str.size(), 0);
    }

private:
    int _sockfd;
};

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2. 简单的使用介绍

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1. 服务端

#include <iostream>
#include <string>
#include <memory>
#include <unistd.h>
#include "Log.hpp"
#include "Socket.hpp"

// ./server localport
int main(int argc, char *argv[])
{
    if(argc != 2)
    {
        std::cout << "Usage: " << argv[0] << "port" << std::endl;
        return 0;
    }
    uint16_t localport = std::stoi(argv[1]);

    std::unique_ptr<TcpSocket> tsvr(new TcpSocket());
    tsvr->BuildListenSocketMethod(localport, backlog);
    while(true)
    {
        std::string peerip;
        uint16_t peerport;
        lg.LogMessage(Debug, "ready to accept, listensocketfd: %d\n", tsvr->GetSockFd());
        Socket *newsock = tsvr->AcceptConnection(&peerip, &peerport);
        if(newsock == nullptr) continue;
        lg.LogMessage(Info, "get a new link... sockfd: %d, client info: %s:%d\n", newsock->GetSockFd(), peerip.c_str(), peerport);
        
        while(true)
        {
            std::string buffer;
            newsock->Recv(&buffer, 1024);
            std::cout << "get a message: " << buffer.c_str() << std::endl;
            sleep(1);
        }

        // 注意资源的释放
        newsock->CloseSocket();
        delete newsock;
    }

    tsvr->CloseSocket();
    return 0;
}

2. 客户端

#include <iostream>
#include <unistd.h>
#include <memory>
#include "Socket.hpp"

// ./client serverip serverport
int main(int argc, char* argv[])
{
    if(argc != 3)
    {
        std::cout << "Usage: " << argv[0] << " serverip serverport" << std::endl;
        return 0;
    }
    std::string serverip = argv[1];
    uint16_t serverport = std::stoi(argv[2]);

    std::unique_ptr<TcpSocket> tsvr(new TcpSocket());
    if(!tsvr->BuildConnectSocketMethod(serverip, serverport))
    {
        std::cerr << "connect " << serverip << ":" << serverport << " failed" << std::endl;
        return 0;
    }
    std::cout << "connect " << serverip << ":" << serverport << " success" << std::endl;

    std::string message = "a";
    char n = 'b';
    while(true)
    {
        tsvr->Send(message);
        message.push_back(n++);
        sleep(1);
    }

    tsvr->CloseSocket();
    return 0;
}

3. 通信测试

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