An Epoll example -- server and client

/* * ===================================================================================== * *       Filename:  tcp_server_epoll.c * *    Description:   * *        Version:  1.0 *        Created:  10/25/2014 10:01:03 PM *       Revision:  none *       Compiler:  gcc * *         Author:  Wei Yang (weiyang), [e-mail] *        Company:   * * ===================================================================================== */#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <string.h>#include <fcntl.h>#include <sys/epoll.h>#include <netdb.h>#include <errno.h>#define MAXEVENTS 64static int socket_fd, epoll_fd;static void socket_create_bind_local(){struct sockaddr_in server_addr;int opt = 1;        if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {            perror("Socket");            exit(1);        }        if (setsockopt(socket_fd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(int)) == -1) {            perror("Setsockopt");            exit(1);        }               server_addr.sin_family = AF_INET;                server_addr.sin_port = htons(5000);            server_addr.sin_addr.s_addr = INADDR_ANY;        bzero(&(server_addr.sin_zero),8);        if (bind(socket_fd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr))                                                                       == -1) {            perror("Unable to bind");            exit(1);        }}static int make_socket_non_blocking(int sfd){int flags;flags = fcntl(sfd, F_GETFL, 0);if (flags == -1) {perror("fcntl");return -1;}flags |= O_NONBLOCK;if (fcntl(sfd, F_SETFL, flags) == -1) {perror("fcntl");return -1;}return 0;}void accept_and_add_new(){struct epoll_event event;struct sockaddr in_addr;socklen_t in_len = sizeof(in_addr);int infd;char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];while ((infd = accept(socket_fd, &in_addr, &in_len)) != -1) {if (getnameinfo(&in_addr, in_len,hbuf, sizeof(hbuf),sbuf, sizeof(sbuf),NI_NUMERICHOST | NI_NUMERICHOST) == 0) {printf("Accepted connection on descriptor %d (host=%s, port=%s)\n",infd, hbuf, sbuf);}/* Make the incoming socket non-block * and add it to list of fds to * monitor*/if (make_socket_non_blocking(infd) == -1) {abort();}event.data.fd = infd;event.events = EPOLLIN | EPOLLET;if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, infd, &event) == -1) {perror("epoll_ctl");abort();}in_len = sizeof(in_addr);}if (errno != EAGAIN && errno != EWOULDBLOCK)perror("accept");/* else * * We hae processed all incomming connectioins * */}void process_new_data(int fd){ssize_t count;char buf[512];while ((count = read(fd, buf, sizeof(buf) - 1))) {if (count == -1) {/* EAGAIN, read all data */if (errno == EAGAIN)return;perror("read");break;}/* Write buffer to stdout */buf[count] = '\0';printf("%s \n", buf);}printf("Close connection on descriptor: %d\n", fd);close(fd);}int main(){struct epoll_event event, *events;socket_create_bind_local();if (make_socket_non_blocking(socket_fd) == -1)exit(1);               if (listen(socket_fd, 5) == -1) {            perror("Listen");            exit(1);        }  printf("\nTCPServer Waiting for client on port 5000\n");        fflush(stdout);epoll_fd = epoll_create1(0);if (epoll_fd == -1) {perror("epoll_create1");exit(1);}event.data.fd = socket_fd;event.events = EPOLLIN | EPOLLET;if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, socket_fd, &event) == -1) {perror("epoll_ctl");exit(1);}events = calloc(MAXEVENTS, sizeof(event));while(1) {int n, i;n = epoll_wait(epoll_fd, events, MAXEVENTS, -1);for (i = 0; i < n; i++) {if (events[i].events & EPOLLERR || events[i].events & EPOLLHUP ||    !(events[i].events & EPOLLIN)) {/* An error on this fd or socket not ready */perror("epoll error");close(events[i].data.fd);} else if (events[i].data.fd == socket_fd) {/* New incoming connection */accept_and_add_new();} else {/* Data incoming on fd */process_new_data(events[i].data.fd);}}}free(events);close(socket_fd);return 0;}

<pre name="code" class="cpp">/* * ===================================================================================== * *       Filename:  tcp_client_epoll.c * *    Description:   * *        Version:  1.0 *        Created:  10/25/2014 10:00:01 PM *       Revision:  none *       Compiler:  gcc * *         Author:  Wei Yang (weiyang), [e-mail] *        Company:   * * ===================================================================================== */#include <sys/socket.h>#include <sys/types.h>#include <netinet/in.h>#include <netdb.h>#include <stdio.h>#include <string.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>int main(){int sock; char send_data[1024];struct hostent *host;struct sockaddr_in server_addr; host = gethostbyname("127.0.0.1");if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {    perror("Socket");    exit(1);}server_addr.sin_family = AF_INET;    server_addr.sin_port = htons(5000);  server_addr.sin_addr = *((struct in_addr *)host->h_addr);bzero(&(server_addr.sin_zero),8);if (connect(sock, (struct sockaddr *)&server_addr,    sizeof(struct sockaddr)) == -1){    perror("Connect");    exit(1);}while(1) {printf("\nSEND (q or Q to quit) : ");gets(send_data);if (strcmp(send_data , "q") != 0 && strcmp(send_data , "Q") != 0)send(sock,send_data,strlen(send_data), 0);elsebreak;}close(sock);return 0;}