select函数实现高性能IO多路访问的关键示例深入解析

#include <sys/select.h>
int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);

void FD_ZERO(fd_set *set);

void FD_SET(int fd, fd_set *set);

void FD_CLR(int fd, fd_set *set);

int FD_ISSET(int fd, fd_set *set);

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <sys/time.h>
#include <unistd.h>
int main(int argc, char const *argv[])
{
    //1.socket创建套接字
    int socked = socket(AF_INET, SOCK_STREAM, 0);
    if (socked < 0)
    {
        perror("socket is err");
        return -1;
    }
    //2.bind绑定服务器ip地址和端口号
    struct sockaddr_in saddr, caddr;
    saddr.sin_family = AF_INET;
    saddr.sin_port = htons(atoi(argv[1]));
    saddr.sin_addr.s_addr = inet_addr("0.0.0.0");
    int len = sizeof(caddr);
    int ret = bind(socked, (struct sockaddr *)(&saddr), sizeof(saddr));
    if (ret < 0)
    {
        perror("bind is err");
        return -1;
    }
    //3.listen设置同时最大链接数
    ret = listen(socked, 5);
    if (ret < 0)
    {
        perror("listen is err");
        return -1;
    }
    //4.select前置工作
    fd_set readfds, tempfds; //创建表
    FD_ZERO(&readfds);       //清空表
    FD_SET(socked, &readfds); //添加文件描述符
    FD_SET(0, &readfds);
    int maxfd = socked, size = 0, maxi = -1, client[1024] = {0};
    char buf[1024] = {0};
    //初始化数组为-1
    for (int i = 0; i < 1024; ++i)
        client[i] = -1;
    while (1)
    {
        tempfds = readfds;
        int ret = select(maxfd + 1, &tempfds, NULL, NULL, NULL);
        if (ret < 0)
        {
            perror("select is err");
            break;
        }
        if (FD_ISSET(socked, &tempfds))
        {
            int fd = accept(socked, (struct sockaddr *)(&caddr), &len);
            printf("port:%d   ip:  %s\n", ntohs(caddr.sin_port), inet_ntoa(caddr.sin_addr));
            //文件描述符加入数组中
            int i;
            for (i = 0; i < 1024; ++i)
            {
                if (client[i] < 0)
                {
                    client[i] = fd;
                    break;
                }
            }
            if (i == 1024)
            {
                printf("too many clients\n");
                exit(-1);
            }
            if (i > maxi)
                maxi = i;
            FD_SET(fd, &readfds);
            if (maxfd < fd)
                maxfd = fd;
            if (--ret == 0)
                continue;
        }
        for (int i = 0; i <= maxi; ++i)
        {
            if (client[i] < 0)
                continue;
            if (FD_ISSET(client[i], &tempfds))
            {
                int flage = recv(client[i], buf, sizeof(buf), 0);
                if (flage < 0)
                {
                    perror("recv is err");
                }
                else if (flage == 0)
                {
                    printf("ip:%s is close\n", inet_ntoa(caddr.sin_addr));
                    close(i);
                    FD_CLR(i, &readfds);
                    client[i] = -1;
                }
                else
                {
                    size = strlen(buf);
                    for (int i = 0; i < size; ++i)
                    {
                        if (buf[i] >= 'a' && buf[i] <= 'z')
                            buf[i] = buf[i] + ('A' - 'a');
                        else
                            buf[i] = buf[i] + ('a' - 'A');
                    }
                    printf("%s\n", buf);
                    send(client[i], buf, sizeof(buf), 0);
                }
                if (--ret == 0)
                    break;
            }
        }
    }
    close(socked);
    return 0;
}

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char const *argv[])
{
    //1.socket建立文件描述符
    int fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0)
    {
        perror("socket is err");
    }
    //2.connect连接服务器
    struct sockaddr_in saddr;
    saddr.sin_family = AF_INET;
    saddr.sin_port = htons(atoi(argv[2]));
    saddr.sin_addr.s_addr = inet_addr(argv[1]);
    int flage = connect(fd, (struct sockaddr *)(&saddr), sizeof(saddr));
    if (flage < 0)
    {
        perror("connect is err");
    }
    //3.服务器端不断发送数据,接受服务器转化后的数据
    char buf[1024] = {0};
    while (1)
    {
        //memset(buf,0,sizeof(buf));
        fgets(buf, sizeof(buf), stdin);
        if (strncmp(buf,"quit#",5)==0)
        {
            break;
        }
        if (buf[strlen(buf) - 1] == '\n')
            buf[strlen(buf) - 1] = '\0';
        send(fd, buf, sizeof(buf), 0);
        flage = recv(fd, buf, sizeof(buf), 0);
        if (flage < 0)
        {
            perror("recv is err");
        }
        else
        {
            fprintf(stdout, "%s\n", buf);
        }
    }
    close(fd);
    return 0;
}