多路IO複用--epoll實現

epoll事件有兩種模型：
Edge Triggered(ET) 邊緣觸發，只有數據到來才觸發，不管緩存區中是否還有數據
Level Triggered(LT) 水平觸發，只要有數據就會觸發

server.c

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

#define SERV_PORT  6666
#define MAX_LINE   1024
#define MAX_CONN   50000

int main()
{
	char buf[MAX_LINE];
	int listenfd = Socket(AF_INET,SOCK_STREAM,0);
	int opt = 1;
	setsockopt(listenfd,SOL_SOCKET,SO_REUSEPORT,&opt,sizeof(opt));//設置端口複用
	setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));//設置地址複用
	
	struct sockaddr_in servaddr;
	bzero(&servaddr,sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(SERV_PORT);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	Listen(listenfd, 128);

	int efd = epoll_create(1);//創建紅黑樹樹根
	if(efd < 0)
	{
		perr_exit("epoll_create");
		return -1;
	}
	
	struct epoll_event event;
	event.events = EPOLLIN;
	event.data.fd = listenfd;
	int res = epoll_ctl(efd,EPOLL_CTL_ADD,listenfd,&event);
	if(res < 0)
	{
		perr_exit("epoll_ctl");
		Close(listenfd);
		return -1;
	}
	while (1)
	{
		struct epoll_event revents[MAX_CONN + 1];
		int nready = epoll_wait(efd,revents,MAX_CONN + 1,-1);
		if(nready < 0)
		{
			perr_exit("epoll_wait");
			break;
		}
		int i = 0;
		for(i = 0;i < nready;i++)
		{
			if((revents[i].events & EPOLLIN)&&(revents[i].data.fd == listenfd))
			{
				struct sockaddr_in clientaddr;
				socklen_t clientsize = sizeof(clientaddr);
				bzero(&clientaddr,clientsize);
				int connfd = Accept(listenfd, (struct sockaddr *)&clientaddr, &clientsize);
				int flag = fcntl(connfd,F_GETFL);
				flag |= O_NONBLOCK;
				fcntl(connfd,F_SETFL,flag);
				char buf[16];
				printf("recvfrom %s at %d\n",inet_ntop(AF_INET,&clientaddr.sin_addr,buf,sizeof(buf)),ntohs(clientaddr.sin_port));
				struct epoll_event ev;
				ev.events = EPOLLIN | EPOLLET;	//設置邊沿觸發
				//ev.events = EPOLLIN ;				//默認水平觸發
				ev.data.fd = connfd;
				res = epoll_ctl(efd,EPOLL_CTL_ADD,connfd,&ev);
				if(res < 0)
				{
					perr_exit("epoll_ctl");
					break;
				}
			}
			else
			{
				if(revents[i].events & EPOLLIN)
				{
					while(1)
					{
						memset(buf,0,sizeof(buf));
						int n = Read(revents[i].data.fd, buf, sizeof(buf));
						if(n == 0)//對端關閉
						{
							printf("client[%d] is closed\n",revents[i].data.fd);
							res = epoll_ctl(efd,EPOLL_CTL_DEL,revents[i].data.fd,NULL);//將該文件描述符從紅黑樹摘除
							if(res < 0)
							{
								perr_exit("read");
							}
							Close(revents[i].data.fd);                  //關閉與該客戶端的鏈接
						}
						else if(n < 0)
						{
							if(errno != EWOULDBLOCK && errno != EINTR)
							{
								perr_exit("read");
								res = epoll_ctl(efd, EPOLL_CTL_DEL, revents[i].data.fd, NULL);
                    			Close(revents[i].data.fd);
							}
						}
						else
						{
							printf("len = %d,buf = %s\n",n,buf);
							buf[n] = '\n';
							Write(revents[i].data.fd, buf, n + 1);
						}
					}
				}
			}
		}
	}
	Close(listenfd);
    Close(efd);
	return 0;
}