epoll实现linux进程通信

server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <signal.h>
#include <sys/epoll.h>
#include <errno.h>

#define UNIX_DOMAIN "/tmp/UNIX.domain"


void handler(){

  printf("clean program start
");
  //unlink(UNIX_DOMAIN);
  remove(UNIX_DOMAIN);
  printf("clean end.
");
}

int main(void)
{
  int lsn_fd, apt_fd;
  struct sockaddr_un srv_addr;
  struct sockaddr_un clt_addr;
  socklen_t clt_len;
  int ret;
  int i;
  char recv_buf[1024];
  char send_buf[1024];  

  signal(SIGTERM,handler);  

  //create epoll 
  int epfd,eventfd;
  struct epoll_event   ev,events[1024];

  epfd = epoll_create(1024);

  //create socket to bind local IP and PORT
  lsn_fd = socket(AF_UNIX, SOCK_STREAM, 0);
  ev.data.fd = lsn_fd;
  ev.events = EPOLLIN|EPOLLET;

  epoll_ctl(epfd,EPOLL_CTL_ADD,lsn_fd,&ev);

  if(lsn_fd < 0)
  {
    perror("can't create communication socket!");
    return 1;
  }

  //create local IP and PORT
  srv_addr.sun_family = AF_UNIX;
  strncpy(srv_addr.sun_path, UNIX_DOMAIN, sizeof(srv_addr.sun_path) - 1);
  //unlink(UNIX_DOMAIN);

  //bind sockfd and sockaddr
  ret = bind(lsn_fd, (struct sockaddr*)&srv_addr, sizeof(srv_addr));
  if(ret == -1)
  {
    perror("can't bind local sockaddr!");
    close(lsn_fd);
    unlink(UNIX_DOMAIN);
    return 1;
  }

  //listen lsn_fd, try listen 5

  ret = listen(lsn_fd, 5);
  if(ret == -1)
  {
    perror("can't listen client connect request");
    close(lsn_fd);
    unlink(UNIX_DOMAIN);

    return 1;
  }

  clt_len = sizeof(clt_addr);
  while(1)
  {
    int nfds = epoll_wait(epfd,events,1024,100);
    int i=0;
    for(i=0;i<nfds;++i)
    {
      if(events[i].data.fd == lsn_fd)
      {
        apt_fd = accept(lsn_fd, (struct sockaddr*)&clt_addr, &clt_len);
        if(apt_fd < 0){
          perror("can't listen client connect request");
          close(lsn_fd);
          unlink(UNIX_DOMAIN);
          return 1; 
        }
        char lines[256];
        sprintf(lines,"server data  to client
");
        write(apt_fd, lines, 256);

        ev.data.fd = apt_fd;
        ev.events = EPOLLIN|EPOLLET;

        epoll_ctl(epfd,EPOLL_CTL_ADD,apt_fd,&ev);

      }
      else if (events[i].events & EPOLLIN) 
      //write数据
      {
        printf("EPOLLIN
");
        if( (eventfd = events[i].data.fd) < 0 )
          continue;

        int n=0,ret=0 ;
        char line[256];
        if ((ret = read(eventfd,line,256)) < 0){

          if(errno == ECONNRESET){
            close(eventfd);
            events[i].data.fd = -1;
          }
          else
            printf("readline error
");
        }
        else if( ret == 0){
          close(eventfd);
          events[i].data.fd = -1;
        }
        else if( ret > 0 )
        {
          line[ret] = '';
          printf("%s",line);
          while( ( ret = read(eventfd,line,256)) >0)
          {
                line[ret] = '';
                printf("%s",line);
          }
          printf("
");
        }
      }
      else if (events[i].events & EPOLLOUT){
        //写出的数据,在EPOLLIN处理中设置fd的events为EPOLLOUT|EPOLLET时,即触发该事件
        int eventfd  = events[i].data.fd;
        char line[256];
        write(eventfd,line,256);

        ev.data.fd = eventfd;
        ev.events = EPOLLIN | EPOLLET;

        epoll_ctl ( epfd, EPOLL_CTL_ADD, eventfd, &ev);
      }
    }
  }

  close(apt_fd);
  close(lsn_fd);
  unlink(UNIX_DOMAIN);
  return 0;
}

client.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#define UNIX_DOMAIN "/tmp/UNIX.domain"

int main(void)
{
  int connect_fd;
  struct sockaddr_un srv_addr;
  char snd_buf[256];
  char rcv_buf[256];
  int ret;
  int i;
  connect_fd = socket(AF_UNIX, SOCK_STREAM, 0);

  if(connect_fd < 0)
  {
    perror("client create socket failed");
    return 1;
  }
  srv_addr.sun_family = AF_UNIX;
  strcpy(srv_addr.sun_path, UNIX_DOMAIN);
  ret = connect(connect_fd, (struct sockaddr*)&srv_addr, sizeof(srv_addr));

  if(ret == -1)
  {
    perror("connect to server failed!");
    close(connect_fd);
    unlink(UNIX_DOMAIN);
    return 1;
  }

  memset(rcv_buf, 0, 256);
  int rcv_num = read(connect_fd, rcv_buf, sizeof(rcv_buf));
  printf("receive message from server (%d) :%s
", rcv_num, rcv_buf);

  memset(snd_buf, 0, 256);
  strcpy(snd_buf, "message from client");
  printf("sizeof(snd_buf): %d
", sizeof(snd_buf));

  printf("send data to server... ...
");
  for(i = 0; i < 4; i++)
  {
    write(connect_fd, snd_buf, sizeof(snd_buf));
  }
  printf("send end!
");
  close(connect_fd);
  return 0;

}

与网络的socket通信的区别，即socket地址有些区别，其他的一样。

sockaddr_in用于网络的socket通信，sockaddr_un用于本机上的进程之间的通信。