（转）浅析epoll – epoll例子以及分析

原文地址：http://www.cppfans.org/1419.html

浅析epoll – epoll例子以及分析

上篇我们讲到epoll的函数和性能。这一篇用用这些个函数，给出一个最简单的epoll的例子。

//
// a simple echo server using epoll in linux
//
// 2009-11-05
// by sparkling
//
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <iostream>
using namespace std;
 
#define MAX_EVENTS 500
 
struct myevent_s
{
    int fd;
    void (*call_back)(int fd, int events, void *arg);
    int events;
    void *arg;
    int status; // 1: in epoll wait list, 0 not in
    char buff[128]; // recv data buffer
    int len;
    long last_active; // last active time
};
 
// set event
void EventSet(myevent_s *ev, int fd, void (*call_back)(int, int, void*), void *arg)
{
    ev->fd = fd;
    ev->call_back = call_back;
    ev->events = 0;
    ev->arg = arg;
    ev->status = 0;
    ev->last_active = time(NULL);
}
 
// add/mod an event to epoll
void EventAdd(int epollFd, int events, myevent_s *ev)
{
    struct epoll_event epv = {0, {0}};
    int op;
    epv.data.ptr = ev;
    epv.events = ev->events = events;
    if(ev->status == 1){
        op = EPOLL_CTL_MOD;
    }
    else{
        op = EPOLL_CTL_ADD;
        ev->status = 1;
    }
    if(epoll_ctl(epollFd, op, ev->fd, &epv) < 0)
        printf("Event Add failed[fd=%d]/n", ev->fd);
    else
        printf("Event Add OK[fd=%d]/n", ev->fd);
}
 
// delete an event from epoll
void EventDel(int epollFd, myevent_s *ev)
{
    struct epoll_event epv = {0, {0}};
    if(ev->status != 1) return;
    epv.data.ptr = ev;
    ev->status = 0;
    epoll_ctl(epollFd, EPOLL_CTL_DEL, ev->fd, &epv);
}
 
int g_epollFd;
myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd
void RecvData(int fd, int events, void *arg);
void SendData(int fd, int events, void *arg);  
// accept new connections from clients
void AcceptConn(int fd, int events, void *arg)
{
    struct sockaddr_in sin;
    socklen_t len = sizeof(struct sockaddr_in);
    int nfd, i;
    // accept
    if((nfd = accept(fd, (struct sockaddr*)&sin, &len)) == -1)
    {
        if(errno != EAGAIN && errno != EINTR)
        {
            printf("%s: bad accept", __func__);
        }
        return;
    }
    do
    {
        for(i = 0; i < MAX_EVENTS; i++)
        {
            if(g_Events[i].status == 0)
            {
                break;
            }
        }
        if(i == MAX_EVENTS)
        {
            printf("%s:max connection limit[%d].", __func__, MAX_EVENTS);
            break;
        }
        // set nonblocking
        if(fcntl(nfd, F_SETFL, O_NONBLOCK) < 0) break;
        // add a read event for receive data
        EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]);
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, &g_Events[i]);
        printf("new conn[%s:%d][time:%d]/n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port), g_Events[i].last_active);
    }while(0);
}
 
// receive data
void RecvData(int fd, int events, void *arg)
{
    struct myevent_s *ev = (struct myevent_s*)arg;
    int len;
    // receive data
    len = recv(fd, ev->buff, sizeof(ev->buff)-1, 0);
    EventDel(g_epollFd, ev);
    if(len > 0)
    {
        ev->len = len;
        ev->buff[len] = '/0';
        printf("C[%d]:%s/n", fd, ev->buff);
        // change to send event
        EventSet(ev, fd, SendData, ev);
        EventAdd(g_epollFd, EPOLLOUT|EPOLLET, ev);
    }
    else if(len == 0)
    {
        close(ev->fd);
        printf("[fd=%d] closed gracefully./n", fd);
    }
    else
    {
        close(ev->fd);
        printf("recv[fd=%d] error[%d]:%s/n", fd, errno, strerror(errno));
    }
}  
// send data
void SendData(int fd, int events, void *arg)
{
    struct myevent_s *ev = (struct myevent_s*)arg;
    int len;
    // send data
    len = send(fd, ev->buff, ev->len, 0);
    ev->len = 0;
    EventDel(g_epollFd, ev);
    if(len > 0)
    {
        // change to receive event
        EventSet(ev, fd, RecvData, ev);
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, ev);
    }
    else
    {
        close(ev->fd);
        printf("recv[fd=%d] error[%d]/n", fd, errno);
    }
}  
void InitListenSocket(int epollFd, short port)
{
    int listenFd = socket(AF_INET, SOCK_STREAM, 0);
    fcntl(listenFd, F_SETFL, O_NONBLOCK); // set non-blocking
    printf("server listen fd=%d/n", listenFd);
    EventSet(&g_Events[MAX_EVENTS], listenFd, AcceptConn, &g_Events[MAX_EVENTS]);
    // add listen socket
    EventAdd(epollFd, EPOLLIN|EPOLLET, &g_Events[MAX_EVENTS]);
    // bind & listen
    sockaddr_in sin;
    bzero(&sin, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = INADDR_ANY;
    sin.sin_port = htons(port);
    bind(listenFd, (const sockaddr*)&sin, sizeof(sin));
    listen(listenFd, 5);
}  
int main(int argc, char **argv)
{
    short port = 12345; // default port
    if(argc == 2){
        port = atoi(argv[1]);
    }
    // create epoll
    g_epollFd = epoll_create(MAX_EVENTS);
    if(g_epollFd <= 0) printf("create epoll failed.%d/n", g_epollFd);
    // create & bind listen socket, and add to epoll, set non-blocking
    InitListenSocket(g_epollFd, port);
    // event loop
    struct epoll_event events[MAX_EVENTS];
    printf("server running:port[%d]/n", port);
    int checkPos = 0;
    while(1){
        // a simple timeout check here, every time 100, better to use a mini-heap, and add timer event
        long now = time(NULL);
        for(int i = 0; i < 100; i++, checkPos++) // doesn't check listen fd
        {
            if(checkPos == MAX_EVENTS) checkPos = 0; // recycle
            if(g_Events[checkPos].status != 1) continue;
            long duration = now - g_Events[checkPos].last_active;
            if(duration >= 60) // 60s timeout
            {
                close(g_Events[checkPos].fd);
                printf("[fd=%d] timeout[%d--%d]./n", g_Events[checkPos].fd, g_Events[checkPos].last_active, now);
                EventDel(g_epollFd, &g_Events[checkPos]);
            }
        }
        // wait for events to happen
        int fds = epoll_wait(g_epollFd, events, MAX_EVENTS, 1000);
        if(fds < 0){
            printf("epoll_wait error, exit/n");
            break;
        }
        for(int i = 0; i < fds; i++){
            myevent_s *ev = (struct myevent_s*)events[i].data.ptr;
            if((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN)) // read event
            {
                ev->call_back(ev->fd, events[i].events, ev->arg);
            }
            if((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT)) // write event
            {
                ev->call_back(ev->fd, events[i].events, ev->arg);
            }
        }
    }
    // free resource
    return 0;
}

上面是一个echo server的例子，下来我们看下echo client的例子

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

#define MAXDATASIZE 100 // max number of bytes we can get at once

int main(int argc, char *argv[])
{
	int sockfd, numbytes;
	char buf[MAXDATASIZE];
	struct hostent *he;
	struct sockaddr_in their_addr; // connector'saddress information

	if (( argc == 1) || (argc==2) )
	{
		fprintf(stderr,"usage: client hostname\nEx:\n$./client01 ip port\n");
		exit(1);
	}

	if ((he=gethostbyname(argv[1])) == NULL)
	{ // get the host info
		herror("gethostbyname");
		exit(1);
	}

	if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)
	{
		perror("socket");
		exit(1);
	}

	their_addr.sin_family = AF_INET; // host byte order
	their_addr.sin_port = htons(atoi(argv[2])); // short, network byte order
	their_addr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(their_addr.sin_zero, '', sizeof their_addr.sin_zero);

	if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof their_addr) == -1)
	{
		perror("connect");
		exit(1);
	}

	while( 1 )
	{
		if(send(sockfd, "hello, this is client message!", strlen("hello, this is client message!"), 0 ) == -1)
		{
			perror("send");
		}

		if ((numbytes=recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
		{
			perror("recv");
		}
		else if( numbytes == 0 )
		{
			printf("Remote server has shutdown!\n");
			break;
		}

		buf[numbytes] = '';

		printf("Received: %s \n",buf);
		sleep(1);
	}

	close(sockfd);
	return 0;
}

以上客户端和服务器例子均来自网络，自己没有单独写，因为觉得自己写了跟着个差不多还浪费时间，大家有兴趣可以去研究下libevent和libev，这都是很好用的C风格的epoll网络库，或者之际看ASIO吧。