网络编程服务器基础模型四(epoll模型)

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdlib.h>

#define SERV_PORT 5358
#define MAX_CONN 1024
#define EVENT_NUM 1024
#define EPOLL_SIZE 1024
#define BUF_LEN 1024

int setnonblocking(int fd){
    int opts;
    if((opts = fcntl(fd, F_GETFL)) < 0){
        return -1;
    }
    opts |=O_NONBLOCK;
    if(fcntl(fd, F_SETFL, opts) < 0){
        return -1;
    }
    return 0;
}

void *str_echo(void *arg){
    int sockfd;
    ssize_t nread;
    char buf[BUF_LEN] = {0};
    pthread_detach(pthread_self());

    sockfd = *(int *)arg;
    while(1) {
        bzero(buf, BUF_LEN);
        if((nread = read(sockfd, buf, BUF_LEN)) == -1) {
            if(errno == EINTR) {
                continue;
            }
            else {
                printf("read error: %s\n", strerror(errno));
                continue;
            }
        }
        else if (nread == 0) {
            break;
        }
        else {
            //fputs(buf, stdout);

            write(sockfd, buf, nread);
        }
    }
    return NULL;    
}

int main(int argc, char **argv)
{
    int listenfd, connfd, epfd, nfds;
    socklen_t addrlen;
    struct sockaddr_in cliaddr, servaddr;
    struct epoll_event ev, events[EVENT_NUM];
    pthread_t tid;

    //create socket fd

    if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        printf("Create socket error!\n");
        return 0;
    }
    if (setnonblocking(listenfd) == -1){
        printf("setnonblicking error!\n");
        close(listenfd);
        return 0;
    }

    //bind

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);
    if(bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1){
        printf("Socket bind error!\n");
        close(listenfd);
        return 0;
    }

    //listen

    if(listen(listenfd, MAX_CONN) == -1){
        printf("listen error\n");
        close(listenfd);
        return 0;
    }

    //create epoll

    if((epfd = epoll_create(EPOLL_SIZE)) == -1){
        printf("Create epoll error!\n");
        close(listenfd);
        return 0;
    }

    //register epoll event

    ev.data.fd = listenfd;
    ev.events = EPOLLIN | EPOLLET;
    if ((epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev)) == -1){
        printf("epoll_ctl error!\n");
        close(listenfd);
        return 0;
    }

    while(1){
        if((nfds = epoll_wait(epfd, events, EVENT_NUM, -1)) ==-1){
            if(errno == EINTR){
                printf("%s\n", strerror(errno));
                continue;
            }
            else{
                printf("epoll_wait error!\n");
                continue;
            }
        }
        int i;
        for(i=0;i<nfds;i++){
            if(events[i].data.fd == listenfd){
                addrlen = sizeof(cliaddr);
                connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &addrlen);
                if(connfd == -1){
                    printf("%s\n", strerror(errno));
                    continue;
                }
                
                printf("New Connection %d\n", connfd);
                ev.data.fd = connfd;
                ev.events = EPOLLIN | EPOLLET;
                if((epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev)) == -1){
                    printf("connect failed!\n");
                }
            }
            else{
                if((pthread_create(&tid, NULL, str_echo, &events[i].data.fd)) == -1) {
                    exit(0);
                }
            }
        }

    }
    return 0;
}

epoll是poll的变种，相对于select，epoll有两种工作模式,ET和LT。

为何ET模式要和非阻塞I/O配合工作

因为在read的时候有可能导致阻塞。解决办法是

1、采用非阻塞I/O直到返回EAGAIN

2、采用多线程