IO复用/ECHO

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

#define MAX_EVENT_NUM 1024
#define TCP_BUFFER_SIZE 512
#define UDP_BUFFER_SIZE 1024

int setnonblocking(int fd)//设置非阻塞;
{
    int oldopt=fcntl(fd,F_GETFL);
    int newopt=oldopt|O_NONBLOCK;
    fcntl(fd,F_SETFL,newopt);
    return oldopt;
}

void addfd(int epollfd,int fd)
{
    epoll_event eve;
    eve.data.fd=fd;
    eve.events=EPOLLIN|EPOLLET;//ET
    epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&eve);
    setnonblocking(fd);
}

int main(int argc,char *argv[])
{
    const char *ip=argv[1];
    int port=atoi(argv[2]);

    int ret=0;
    struct sockaddr_in address;
    bzero(&address,sizeof(address));
    address.sin_family=AF_INET;
    inet_pton(AF_INET,ip,&address.sin_addr);
    address.sin_port=htons(port);
    int listenfd=socket(PF_INET,SOCK_STREAM,0);

    ret=bind(listenfd,(struct sockaddr*)&address,sizeof(address));
    ret=listen(listenfd,5);

    epoll_event events[MAX_EVENT_NUM];
    int epollfd=epoll_create(5);
    addfd(epollfd,listenfd);

    while(1)
    {
        int num=epoll_wait(epollfd,events,MAX_EVENT_NUM,-1);
        if(num<0)
        {
            printf("epoll falied\n");
            break;
        }

        for(int i=0;i<num;i++)
        {
            int sockfd=events[i].data.fd;
            if(sockfd==listenfd)
            {
                struct sockaddr_in client_addr;
                socklen_t client_addrlen=sizeof(client_addr);
                int connfd=accept(listenfd,(struct sockaddr*)&client_addr,&client_addrlen);
                addfd(epollfd,connfd);
            }
            else if(events[i].events&EPOLLIN)
            {
                char buf[TCP_BUFFER_SIZE];
                while(1)
                {
                    memset(buf,0,TCP_BUFFER_SIZE);
                    ret=recv(sockfd,buf,TCP_BUFFER_SIZE-1,0);
                    if(ret<0)
                    {
                        if((errno==EAGAIN)||(errno==EWOULDBLOCK))//表示数据已经全部读取完毕，此后epoll就能再次触发该socket上的EPOLLIN事件;
                        {
                            break;
                        }
                        close(sockfd);
                        break;
                    }
                    else if(ret==0)//客户端关闭连接;
                    {
                        close(sockfd);
                    }
                    else
                        send(sockfd,buf,ret,0);
                }
            }
            else
            {
                printf("somethins else happen\n");
            }
        }
    }
    close(listenfd);
    return 0;
}