epoll-13-socketpair.cpp

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>

#define EVENTS 8

int soc[2];

void processA(){
  sleep(3);
  printf("processA: send message\n");
  write(soc[0], "HELLO\n", 6);
  return;
}

void processB(){
  int epfd;
  epoll_event ev, ev_ret[EVENTS];
  int nfds;
  int i;
  char buf[128];

  epfd = epoll_create(1);
  if(epfd < 0){
    perror("epoll_create");
    return ;
  }

  memset(&ev, 0, sizeof(ev));
  ev.events = EPOLLIN;
  ev.data.fd = soc[1];

  if(epoll_ctl(epfd, EPOLL_CTL_ADD, soc[1], &ev) != 0){
    perror("epoll_clt");
    return ;
  }

  memset(&ev, 0, sizeof(ev));
  ev.events = EPOLLIN;
  ev.data.fd = fileno(stdin);

  if(epoll_ctl(epfd, EPOLL_CTL_ADD, fileno(stdin), &ev) != 0){
    perror("epoll_clt1");
    return ;
  }

  while(1){
    printf("before epoll_wait\n");

    nfds = epoll_wait(epfd, ev_ret, EVENTS , -1);
    if(nfds < 0){
      perror("epoll_wait");
      return;
    }

    printf("after epoll_wait\n");

    for(i = 0; i < nfds; ++i){
      if(ev_ret[i].data.fd == soc[1]){
	printf("processB:break message from socketpair\n");
	goto outofloop;
      }
      else if(ev_ret[i].data.fd == fileno(stdin)){
	read(fileno(stdin), buf, sizeof(buf));
	printf("processB:input from stdin\n");
      }
    }
  }

 outofloop:
  printf("process B:outside of loop\n");

  return ;
}
int main(){
  int ret;

  ret = socketpair(AF_UNIX, SOCK_STREAM, 0, soc);
  if(ret != 0){
    perror("socketpair");
    return 1;
  }

  if(fork() == 0){
    processA();
  }
  else{
    processB();
  }

  return 0;
}