epoll_server.c

//epoll_server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/epoll.h>

#define BUF_SIZE 100
#define EPOLL_SIZE 50
void error_handling(char *buf);

int main(int
 
 argc, char *argv[])
{
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_adr, clnt_adr;
    socklen_t adr_sz;
    int str_len, i;
    char buf[BUF_SIZE];

    struct epoll_event *ep_events;
    struct epoll_event event;
    int epfd, event_cnt;

    if(argc!=2) {
        printf("Usage : %s <port>\n
 
", argv[0]);
        exit(1);
    }

    serv_sock=socket(PF_INET, SOCK_STREAM, 0);
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family=AF_INET;
    serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
    serv_adr.sin_port=htons(atoi(argv[1]));

    if(bind(serv_sock, (struct sockaddr*) &serv_adr, sizeof
 
(serv_adr))==-1)
        error_handling("bind() error");
    if(listen(serv_sock, 5)==-1)
        error_handling("listen() error");

    epfd=epoll_create(EPOLL_SIZE);
    ep_events=malloc(sizeof(struct epoll_event)*EPOLL_SIZE);

    event.events=EPOLLIN;
    event.data.fd=serv_sock;  
    epoll_ctl(epfd, EPOLL_CTL_ADD, serv_sock, &event);

    while(1)
    {
        event_cnt=epoll_wait(epfd, ep_events, EPOLL_SIZE, -1);
        if(event_cnt==-1)
        {
            puts("epoll_wait() error");
            break;
        }

        for(i=0; i<event_cnt; i++)
        {
            if(ep_events[i].data.fd==serv_sock)
            {
                adr_sz=sizeof(clnt_adr);
                clnt_sock=
                    accept(serv_sock, (struct sockaddr*)&clnt_adr, &adr_sz);
                event.events=EPOLLIN;
                event.data.fd=clnt_sock;
                epoll_ctl(epfd, EPOLL_CTL_ADD, clnt_sock, &event);
                printf("connected client: %d \n", clnt_sock);
            }
            else
            {
                str_len=read(ep_events[i].data.fd, buf, BUF_SIZE);
                if(str_len==0)    // close request!
                {
                    epoll_ctl(
                            epfd, EPOLL_CTL_DEL, ep_events[i].data.fd, NULL);
                    close(ep_events[i].data.fd);
                    printf("closed client: %d \n", ep_events[i].data.fd);
                }
                else
                {
                    write(ep_events[i].data.fd, buf, str_len);    // echo!
                }

            }
        }
    }
    close(serv_sock);
    close(epfd);
    return 0;
}

void error_handling(char *buf)
{
    fputs(buf, stderr);
    fputc('\n', stderr);
    exit(1);
}

epoll_client.c

//epoll_client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 1024
void error_handling(char *message);

int main(int argc, char *argv[])
{
    int sock;
    char message[BUF_SIZE];
    int str_len;
    struct sockaddr_in serv_adr;

    if(argc!=3) {
        printf("Usage : %s <IP> <port>\n", argv[0]);
        exit(1);
    }

    sock=socket(PF_INET, SOCK_STREAM, 0);  
    if(sock==-1)
        error_handling("socket() error");

    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family=AF_INET;
    serv_adr.sin_addr.s_addr=inet_addr(argv[1]);
    serv_adr.sin_port=htons(atoi(argv[2]));

    if(connect(sock, (struct sockaddr*)&serv_adr, sizeof(serv_adr))==-1)
        error_handling("connect() error!");
    else
        puts("Connected...........");

    while(1)
    {
        fputs("Input message(Q to quit): ", stdout);
        fgets(message, BUF_SIZE, stdin);

        if(!strcmp(message,"q\n") || !strcmp(message,"Q\n"))
            break;

        write(sock, message, strlen(message));
        str_len=read(sock, message, BUF_SIZE-1);
        message[str_len]=0;
        printf("Message from server: %s", message);
    }

    close(sock);
    return 0;
}

void error_handling(char *message)
{
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}