浅析epoll – epoll例子以及分析

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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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