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 onceint main(int argc, char *argv[])
{int sockfd, numbytes;char buf[MAXDATASIZE];struct hostent *he;struct sockaddr_in their_addr; // connector'saddress informationif (( 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 infoherror("gethostbyname");exit(1);}if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {perror("socket");exit(1);}their_addr.sin_family = AF_INET; // host byte ordertheir_addr.sin_port = htons(atoi(argv[2])); // short, network byte ordertheir_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。

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