IO复用之epoll

IO复用

select、poll和epoll是三个常用的IO多路复用方法，具体的差别和性能从左到右都是有区别的。但对于这几种IO复用方法是如何使用的，还是一知半解。

实例

这几天，通过阅读redis的源码，对epoll的使用方法有了进一步的认识。因此，这里使用epoll做一个简单的接受io请求的例子

#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
server.c
int main(int argc , char *argv[])
{
    int epfd, sfd, new_socket, c, count;
    struct sockaddr_in server, client;
    struct epoll_event *events;
    struct epoll_event ee = {0};
    events = (struct epoll_event*)malloc(sizeof(struct epoll_event)*100);
    //Create socket

    sfd = socket(AF_INET , SOCK_STREAM , 0);
    if (sfd == -1)
    {
        printf("Could not create socket");
    }

    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons( 9886);

    //Bind
    if( bind(socket_desc, (struct sockaddr *)&server , sizeof(server)))
    {
        printf("failed to bind");
    }

    //Listen
    listen(sfd, 3);

    // 设置非阻塞
    if (fcntl(socket_desc, F_SETFL, O_NONBLOCK) == -1) {
        printf("set non block faild");
    }

    //创建epoll
    epfd = epoll_create(1024);
    if (epfd == -1) {
        printf("epoll create failed");
    }

    // 为sfd，监听读io
    ee.events |= EPOLLIN;
    if (epoll_ctl(epfd, EPOLL_CTL_ADD, sfd, &ee) == -1) {
        printf("register failed");
    }

    while(1) {
        count = epoll_wait(epfd, events, 100,0);
        if (count > 0) {
        	// 这里其实已经定位到有监听的fd，读io已经就绪，根据count遍历events列表，便可得到实际消息和对应的处理方法
            printf("mo god");
            break;
        }
    }

    return 0;
}

client.c
int main(int argc, char** argv)
{
    int sockfd, n,rec_len;
    char recvline[4096], sendline[4096];
    char buf[MAXLINE];
    char *addr = "127.0.0.1";
    struct sockaddr_in servaddr;

    if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        printf("create socket error: %s(errno: %d)\n", strerror(errno),errno);
        exit(0);
    }

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(9886);
    if( inet_pton(AF_INET, addr, &servaddr.sin_addr) <= 0){ //inet_pton是Linux下IP地址转换函数，将IP地址在“点分十进制”和“整数”之间转换
        printf("inet_pton error for %s\n",argv[1]);
        exit(0);
    }

    if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){
        printf("connect error: %s(errno: %d)\n",strerror(errno),errno);
        exit(0);
    }

    printf("send msg to server: \n");
    fgets(sendline, 4096, stdin);
    if( send(sockfd, sendline, strlen(sendline), 0) < 0)  {
        printf("send msg error: %s(errno: %d)\n", strerror(errno), errno);
        exit(0);
    }
    if((rec_len = recv(sockfd, buf, MAXLINE,0)) == -1) {
       perror("recv error");
       exit(1);
    }
    buf[rec_len]  = '\0';
    printf("Received : %s ",buf);
    close(sockfd);
    exit(0);
}