epoll网络通信-优快云博客

epoll可以说是linux服务器下网络通信的事实标准了，epoll使用简单且性能高，只需要三个函数就可以关联自己感兴趣的套接字(文件描述符)。一个可用的echo回声epoll程序例子如下：

服务器:

#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 <stdlib.h>
#include <string.h>

#define MAXLINE       100
#define LISTENQ       20
#define SERV_PORT   2345

void setnonblocking(int sock)
{
int opts;
opts = fcntl(sock, F_GETFL);

   if(opts < 0) {
       perror("fcntl(sock, GETFL)");
       exit(1);
   }

opts = opts | O_NONBLOCK;

   if(fcntl(sock, F_SETFL, opts) < 0) {
       perror("fcntl(sock, SETFL, opts)");
       exit(1);
   }
}

int main(int argc, char *argv[])
{
   int i, listenfd, connfd, sockfd, epfd, nfds;
   ssize_t n;
   char line[MAXLINE];
   socklen_t clilen;

struct epoll_event ev, events[20];

epfd = epoll_create(256);

struct sockaddr_in clientaddr;
struct sockaddr_in serveraddr;

listenfd = socket(AF_INET, SOCK_STREAM, 0);

//setnonblocking(listenfd);

   ev.data.fd = listenfd;
   ev.events = EPOLLIN | EPOLLET;
   //ev.events = EPOLLIN;

epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev); //注册事件

   bzero(&serveraddr, sizeof(serveraddr));
   serveraddr.sin_family = AF_INET;
   char *local_addr = "127.0.0.1";
   inet_aton(local_addr, &(serveraddr.sin_addr));
   serveraddr.sin_port = htons(SERV_PORT);

bind(listenfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));

listen(listenfd, LISTENQ);

printf("epoll socket begins.\n");

for(; ;) {

nfds = epoll_wait(epfd, events, 20, 500);

for(i = 0; i < nfds; ++i) {
if(events[i].data.fd == listenfd && (events[i].events & EPOLLIN)) {

printf("accept connection, fd is %d\n", listenfd);

connfd = accept(listenfd, (struct sockaddr *)&clientaddr, &clilen);

               if(connfd < 0) {
                   perror("connfd < 0");
                   exit(1);
               }

//setnonblocking(connfd);

char *str = inet_ntoa(clientaddr.sin_addr);
printf("connect from %s\n", str);

               ev.data.fd = connfd;
               //ev.events = EPOLLIN | EPOLLET;
               ev.events = EPOLLIN;
               epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);
           }
           else if(events[i].events & EPOLLIN) {

if((sockfd = events[i].data.fd) < 0) continue;

bzero(line, sizeof(line));

               if((n = read(sockfd, line, MAXLINE)) < 0) {
                   if(errno == ECONNRESET) {
                       close(sockfd);
                       events[i].data.fd = -1;
                   } else {
                       printf("readline error");
                   }
               } else if(n == 0) {
                   close(sockfd);
                   events[i].data.fd = -1;
               }

               printf("received data:%s\n", line);

               ev.data.fd = sockfd;
               //ev.events = EPOLLOUT | EPOLLET;
               ev.events = EPOLLOUT;
               epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev);
           }
           else if(events[i].events & EPOLLOUT) {
               sockfd = events[i].data.fd;
               write(sockfd, line, n);

printf("written data:%s\n", line);

               ev.data.fd = sockfd;
               //ev.events = EPOLLIN | EPOLLET;
               ev.events = EPOLLIN;
               epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev); //水平触发模式下需要变更为可读方式，否则会不停的触发写事件
           }
       }
   }
}

客户端:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <iostream>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>

void setnonblocking(int sock)
{
int opts;
opts = fcntl(sock, F_GETFL);

   if(opts < 0) {
       perror("fcntl(sock, GETFL)");
       exit(1);
   }

opts = opts | O_NONBLOCK;

   if(fcntl(sock, F_SETFL, opts) < 0) {
       perror("fcntl(sock, SETFL, opts)");
       exit(1);
   }
}

int main()
{
//创建套接字
int sock = socket(AF_INET, SOCK_STREAM, 0);

//向服务器（特定的IP和端口）发起请求
struct sockaddr_in serv_addr;
memset(&serv_addr, 0, sizeof(serv_addr)); //每个字节都用0填充
serv_addr.sin_family = AF_INET; //使用IPv4地址
serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); //具体的IP地址
serv_addr.sin_port = htons(2345); //端口
connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));

//setnonblocking(sock);

//读取服务器传回的数据
char buffer[100];
int ret = 0;

   while (1) {
       bzero(buffer, sizeof(buffer));
       std::cout << "input:" << std::endl;
       gets(buffer);
       write(sock, buffer, strlen(buffer));
       bzero(buffer, sizeof(buffer));
       //std::cout << "begin to read" << std::endl;
       ret = read(sock, buffer, sizeof(buffer)-1);
       if (ret == 0) break;
       //std::cout << sizeof(buffer) << " " << strlen(buffer) << " " << ret << std::endl;
       printf("Message form server: %s\n", buffer);
   }

//关闭套接字
close(sock);

return 0;
}