epoll ET模式服务器和客户端源码例子

关于epoll替代select作为高性能服务器的事件通知机制的资料相当多，我就不在这里班门弄斧了，有兴趣的同学可以参考末尾的文献链接。

这里说明如下：

1.epoll是linux下高并发服务器的完美方案，因为是基于事件触发的，所以比select快的不只是一个数量级。

2.单线程epoll，触发量可达到15000，参见文献[4]

3.高性能server要使用非阻塞方式。

使用ET模型的时候，一定要注意，每次收到有效通知，然后读取数据的时候，务必每次读取干净（读到出错为止）。当再次调用check（sockfd）的时候才能正确返回。

目前使用的epoll模型大多都是ET模式，socket都要设置为非阻塞的。

网上找了很多源码例子，但是大多不理想，下面是我根据网上资料修改尝试出的一个例子，供大家参考。后续更进一步地研究可以参考nginx，memcache，Apache traffic server这类开源代码。

epoll服务器端

//compile: g++ -g epoll_server.cpp -o epoll_server
//run: ./epoll_server
//
#include <sys/socket.h>
#include <sys/epoll.h>
#include <sys/sendfile.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <fcntl.h>
#include <errno.h>


#define MAX_EVENTS 10
#define LISTENQ 20
#define PORT 5000 //8080


//设置socket连接为非阻塞模式
void setnonblocking (int fd)
{
	int opts;

	opts = fcntl (fd, F_GETFL);
	if (opts < 0)
	{
		perror ("fcntl(F_GETFL)\n");
		exit (1);
	}
	opts = (opts | O_NONBLOCK);
	if (fcntl (fd, F_SETFL, opts) < 0)
	{
		perror ("fcntl(F_SETFL)\n");
		exit (1);
	}
}

int main ()
{
	struct epoll_event ev, events[MAX_EVENTS];
	int listenfd, connfd, nfds, epfd, sockfd, i, nread, n;
	struct sockaddr_in local, remote;
    socklen_t addrlen;
	char buf[BUFSIZ];

	//创建listen socket
	if ((listenfd = socket (AF_INET, SOCK_STREAM, 0)) < 0)
	{
		perror ("sockfd\n");
		exit (1);
	}
	setnonblocking (listenfd);
	bzero (&local, sizeof (local));
	local.sin_family = AF_INET;
	local.sin_addr.s_addr = htonl (INADDR_ANY);;
	local.sin_port = htons (PORT);
	if (bind (listenfd, (struct sockaddr *) &local, sizeof (local)) < 0)
	{
		perror ("bind\n");
		exit (1);
	}
	listen (listenfd, LISTENQ);

	epfd = epoll_create (MAX_EVENTS);
	if (epfd == -1)
	{
		perror ("epoll_create");
		exit (EXIT_FAILURE);
	}
	ev.events = EPOLLIN;
	ev.data.fd = listenfd;
	if (epoll_ctl (epfd, EPOLL_CTL_ADD, listenfd, &ev) == -1)
	{
		perror ("epoll_ctl: listen_sock");
		exit (EXIT_FAILURE);
	}

	for (;;)
	{
		nfds = epoll_wait (epfd, events, MAX_EVENTS, -1);
		if (nfds == -1)
		{
			perror ("epoll_wait error");
			exit (EXIT_FAILURE);
		}

		for (i = 0; i < nfds; ++i)
		{
			sockfd = events[i].data.fd;
			if (sockfd == listenfd)
			{
				while ((connfd = accept (listenfd, (struct sockaddr *) &remote, &addrlen)) > 0)
				{
                    char *ipaddr = inet_ntoa (remote.sin_addr);
                    printf("accept a connection from [%s]\n", ipaddr);
					setnonblocking (connfd);	//设置连接socket为非阻塞
					ev.events = EPOLLIN | EPOLLET;	//边沿触发要求套接字为非阻塞模式；水平触发可以是阻塞或非阻塞模式
					ev.data.fd = connfd;
					if (epoll_ctl (epfd, EPOLL_CTL_ADD, connfd, &ev) == -1)
					{
						perror ("epoll_ctl: add");
						exit (EXIT_FAILURE);
					}
				}
				if (connfd == -1)
				{
					if (errno != EAGAIN && errno != ECONNABORTED && errno != EPROTO && errno != EINTR)
						perror ("accept");
				}
				continue;
			}
			if (events[i].events & EPOLLIN)
			{
				n = 0;
				while ((nread = read (sockfd, buf + n, BUFSIZ - 1)) > 0)
				{
					n += nread;
				}
				if (nread == -1 && errno != EAGAIN)
				{
					perror ("read error");
				}
                printf("recv from client data [%s]\n", buf);
				ev.data.fd = sockfd;
				ev.events = events[i].events | EPOLLOUT;
				if (epoll_ctl (epfd, EPOLL_CTL_MOD, sockfd, &ev) == -1)
				{
					perror ("epoll_ctl: mod");
				}
			}
			if (events[i].events & EPOLLOUT)
			{
				snprintf (buf, sizeof(buf), "HTTP/1.1 200 OK\r\nContent-Length: %d\r\n\r\nHello World", 11);
				int nwrite, data_size = strlen (buf);
				n = data_size;
				while (n > 0)
				{
					nwrite = write (sockfd, buf + data_size - n, n);
					if (nwrite < n)
					{
						if (nwrite == -1 && errno != EAGAIN)
						{
							perror ("write error");
						}
						break;
					}
					n -= nwrite;
				}
                printf("send to client data [%s]\n", buf);
				close (sockfd);
                events[i].data.fd = -1;
			}
		}
	}
	close (epfd);
	close (listenfd);
	return 0;
}

epoll客户端

//compile: g++ -g epoll_client.cpp -o epoll_client
//run: ./epoll_client
//
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>

using namespace std;

#define PORT 5000

int main(int argc, char* argv[])
{
    int sockfd, on = 1;
    char buffer[512] = {0};
    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));

    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        cout << "create socket fail" << endl;
        return -1;
    }
    cout << "succeed to create client socket fd " << sockfd  << endl;

    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
    cout << "set socket reuse by etsockopt" << endl;

    servaddr.sin_port = htons((short)PORT);
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1"); //此处更改epoll服务器地址

    if(connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){
        cout << "connect error" << endl;
        return -1;
    }
    cout << "succeed to connect epoll server " << endl;

    char target[] = "The Author: [email protected]";
    memcpy(buffer, target, strlen(target));
    int wlen = send(sockfd, buffer, strlen(buffer), 0);
    if(wlen <= 0)
        cout << " send data to server fail " << strerror(errno) << endl;
    cout << "send data to server on success, data: [" << buffer << "]"<< endl;

    memset(buffer, 0, sizeof(buffer));
    int rlen = recv(sockfd, buffer, sizeof(buffer), 0);
    if(rlen <= 0)
        cout << " receive data from server fail " << strerror(errno) << endl;
    cout << "receive data from server on success, data: [" << buffer << "]" << endl;

    return 0;
}

大家可以在上述框架上进一步修改.下面是运行图

下面的参考文献按照我认为的优先级递减排列

[1].http://www.cnblogs.com/aicro/archive/2012/12/27/2836170.html

[2].http://blog.csdn.net/hzhsan/article/details/23650465 

[3].http://blog.csdn.net/ljx0305/article/details/4065058

[4].http://blog.csdn.net/win_lin/article/details/7843000

[5].http://blog.csdn.net/win_lin/article/details/7566466

[6].http://blog.csdn.net/qcghdy/article/details/22791077

[7].http://www.cnblogs.com/iTsihang/archive/2013/05/23/3095775.html

[8].http://www.cppblog.com/API/archive/2013/11/27/204456.html#204479

[9]. http://blog.csdn.net/ljx0305/article/details/4065058