Cpp-Socket网络编程（十）客户端升级为select网络模型

1. 在服务器端加入，如果有新用户连接服务器端则向所有连接的客户端发送消息：

if (FD_ISSET(_sock, &fdRead)) {
    FD_CLR(_sock, &fdRead);
    //4. 等待客户端连接accept
    sockaddr_in clientAddr = {};
    socklen_t nAddrLen = sizeof(sockaddr_in);
    int _cSock = accept(_sock, (sockaddr*)&clientAddr, &nAddrLen); //套接字，收到客户端socket地址，返回socket地址的大小
    if (_cSock == -1) {
        perror("client socket error!\n");
    } else {
        //当新客户端加入时群发给其他客户端
        for (int n = (int)g_clients.size() - 1; n >= 0; --n) {
            NewUserJoin userJoin;
            send(g_clients[n], (const char*)&userJoin, sizeof(NewUserJoin), 0);
        }
                
        g_clients.push_back(_cSock);
        printf("client socket success! socket = %d, IP = %s \n", _cSock, inet_ntoa(clientAddr.sin_addr)); //打印客户端socket和IP地址
    }
}

2. 改造客户端，向其中加入select网络模型：

具体操作与服务器端类似，加入select网络模型，将客户端的消息处理封装到processor函数中。

//
//  client.cpp
//  SocketStepByStep
//
//  Created by 刘君妍 on 2019/7/19.
//  Copyright © 2019 tower. All rights reserved.
//
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define SOCKET_ERROR -1

//三个命令：登入、登出和错误信息
enum CMD {
    CMD_LOGIN,
    CMD_LOGIN_RESULT,
    CMD_LOGOUT,
    CMD_LOGOUT_RESULT,
    CMD_NEW_USER_JOIN,
    CMD_ERROR
};

//包头
struct DataHeader {
    short dataLength; //数据长度
    short cmd; //命令
};

//包体 DataPackage
struct Login : public DataHeader
{
    Login() {
        dataLength = sizeof(Login);
        cmd = CMD_LOGIN;
    }
    char UserName[32];
    char PassWord[32];
};

struct LoginResult : public DataHeader
{
    LoginResult() {
        dataLength = sizeof(LoginResult);
        cmd = CMD_LOGIN;
        result = 0;
    }
    int result;
};

struct LogOut : public DataHeader
{
    LogOut() {
        dataLength = sizeof(LogOut);
        cmd = CMD_LOGOUT;
    }
    char UserName[32];
    
};

struct LogoutResult: public DataHeader
{
    LogoutResult() {
        dataLength = sizeof(LogoutResult);
        cmd = CMD_LOGOUT;
        result = 0;
    }
    int result;
};

struct NewUserJoin: public DataHeader
{
    NewUserJoin() {
        dataLength = sizeof(NewUserJoin);
        cmd = CMD_NEW_USER_JOIN;
        sock = 0;
    }
    int sock;
};

//处理进程
int processor(int _sock) {
    char szRecv[4096] = {}; //缓冲，用于接收数据
    //5. 接收客户端的请求数据
    int nLen = recv(_sock, szRecv, sizeof(DataHeader), 0);
    DataHeader* header = (DataHeader*)szRecv;
    if (nLen <= 0) {
        printf("nLen <= 0, connection with server has quit!\n");
        return -1;
    }

    //6. 处理请求
    switch (header->cmd) {
        //接收服务器返回的数据并存储在szRecv中
        case CMD_LOGIN_RESULT:
        {
            recv(_sock, szRecv + sizeof(DataHeader), header->dataLength - sizeof(DataHeader), 0);
            LoginResult* login = (LoginResult*)szRecv;
            printf("receive fron server: CMD_LOGIN_RESULT, datalength: %d\n", login->dataLength);
        }
            break;
        case CMD_LOGOUT_RESULT:
        {
            recv(_sock, szRecv + sizeof(DataHeader), header->dataLength - sizeof(DataHeader), 0);
            LogoutResult* logout = (LogoutResult*)szRecv;
            printf("receive fron server: CMD_LOGOUT_RESULT, datalength: %d\n", logout->dataLength);
        }
            break;
        case CMD_NEW_USER_JOIN:
        {
            recv(_sock, szRecv + sizeof(DataHeader), header->dataLength - sizeof(DataHeader), 0);
            NewUserJoin* userJoin = (NewUserJoin*)szRecv;
            printf("receive fron server: NEW_USER_JOIN, datalength: %d\n", userJoin->dataLength);
        }
            break;
    }
    return 0;
}

int main() {
    //1. 建立一个socket
    int _sock = socket(AF_INET, SOCK_STREAM, 0); //与服务器端不同，第三个参数无需声明使用TCP连接
    if (_sock == SOCKET_ERROR) {
        printf("socket build error!\n");
    } else {
        printf("socket build success!\n");
    }
    
    //2. 连接服务器
    sockaddr_in _sin = {};
    _sin.sin_family = AF_INET;
    _sin.sin_port = htons(4567);
    _sin.sin_addr.s_addr = inet_addr("127.0.0.1");
    int ret = connect(_sock, (sockaddr*)&_sin, sizeof(sockaddr_in));
    if (ret == SOCKET_ERROR) {
        printf("connect error!\n");
    } else {
        printf("connect success!\n");
    }
    
    while (true) {
        fd_set fdReads; //用于在文件描述符集合中增加一个新的文件描述符。
        FD_ZERO(&fdReads);
        FD_SET(_sock, &fdReads);
        timeval t = {1, 0};
        int ret = select(_sock, &fdReads, 0, 0, &t);
        if (ret < 0) {
            printf("1select task over!\n");
            break;
        }
        if(FD_ISSET(_sock, &fdReads)) { //用于测试指定的文件描述符是否在该集合中。
            FD_CLR(_sock, &fdReads); //用于在文件描述符集合中删除一个文件描述符。
            if(-1 == processor(_sock)) { //processor封装了客户端对服务器端传递而来的数据的处理
                printf("2select task over!\n");
                break;
            }
        }
        
        //客户端主动向服务器端发送数据
        printf("空闲时间处理其他业务……\n");
    }
    
    //7. 关闭套接字close socket
    close(_sock);
    
    printf("client has quit!");
    getchar();
    return 0;
}