epoll (Non Blocking I/O)

server_epoll_tcp.cpp

#include <stdio.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

#define CONCURRENT 10

int main(){
	
	int listen_sock, conn_sock, epoll_fd;
	struct epoll_event event;
	struct epoll_event *events;
	struct sockaddr_in server;
	struct sockaddr_in client;
	fd_set fds, _fds;
	char rbuf[65535];
	char sbuf[] = "Done.";

	listen_sock = socket(AF_INET, SOCK_STREAM, 0);
	if( listen_sock == -1 ){
		fprintf(stderr, "socket() error [%d].", errno);
		return -1;
	}

	server.sin_family = AF_INET;
	server.sin_addr.s_addr = inet_addr("127.0.0.1");
	server.sin_port = htons(11111);

	if( bind(listen_sock, (struct sockaddr *)&server, sizeof(server)) == -1 ){
		fprintf(stderr, "bind() error [%d].", errno);
		return -1;
	}

	int flags = fcntl( listen_sock, F_GETFL, 0 );
	if( flags == -1 ){
		fprintf(stderr,"fcntl error[%d].",errno);
		return -1;
	}
	flags |= O_NONBLOCK;
	if( fcntl( listen_sock, F_SETFL, flags ) == -1 ){
		fprintf(stderr,"fcntl error[%d].",errno);
		return -1;
	}


	if( listen(listen_sock, CONCURRENT) == -1 ){
		fprintf(stderr, "listen() error [%d].", errno);
		return -1;
	}

	epoll_fd = epoll_create1(0);
	if( epoll_fd == -1 ){
		fprintf(stderr,"epoll_create1 error [%d].",errno);
	}

	event.data.fd = listen_sock;
	event.events = EPOLLIN | EPOLLET;
	if( epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_sock, &event) == -1 ){
		fprintf(stderr,"epoll_ctrl error [%d].",errno);
		return -1;
	}

	events = (epoll_event *)calloc(CONCURRENT, sizeof(event));

	int cnt=0;
	int event_cnt=0;
	while(1){

		printf("Wait at epoll_wait #%d.\n", cnt);
		event_cnt=epoll_wait(epoll_fd, events, CONCURRENT, -1);

		int len, size;
		for(int i=0; i<event_cnt; i++){

			if( !(events[i].events & EPOLLIN) ){
				fprintf(stderr, "epoll_wait error [%d].",errno);
				return -1;

			}else if( listen_sock == events[i].data.fd ){
				printf("Connect request(s) received.\n");
	
				while(1){

					len = sizeof(client);
					conn_sock = accept(listen_sock, (struct sockaddr *)&client, (socklen_t *)&len);
					if( conn_sock == -1 ){
						if ( errno == EAGAIN ){
							printf("Processed all incoming connections @ %d.\n", listen_sock);
							break;
						}else{
							fprintf(stderr, "accept error [%d].", errno);
							return -1;
						}
					}
	
					flags = fcntl( conn_sock, F_GETFL, 0 );
					if( flags == -1 ){
						fprintf(stderr,"fcntl error[%d].",errno);
						return -1;
					}
					flags |= O_NONBLOCK;
					if( fcntl( conn_sock, F_SETFL, flags ) == -1 ){
						fprintf(stderr,"fcntl error[%d].",errno);
						return -1;
					}

					event.data.fd = conn_sock;
					event.events = EPOLLIN | EPOLLET;
					if( epoll_ctl( epoll_fd, EPOLL_CTL_ADD, conn_sock, &event) == -1 ){
						fprintf(stderr, "epoll_ctl error [%d].",errno);
						return -1;
					}
					printf("Added %d to epoll instance.\n",conn_sock);

				}

			}else{

				while(1){
					printf("Send request received from %d.\n",events[i].data.fd);
					memset(rbuf, 0, sizeof(rbuf));

					size = recv( events[i].data.fd, rbuf, sizeof(rbuf), 0);
					printf("Received data size %d byte.\n",size);
					if( size == -1 ){

						if ( errno == EAGAIN ){
							printf("Processed all incoming connections @ %d.\n",events[i].data.fd);
							break;
						}else{
							fprintf(stderr, "recv error [%d].", errno);
							return -1;
						}

					}else if( size == 0 ){
						printf("Closed by %d.\n",events[i].data.fd);
						//shutdown(events[i].data.fd, 2);
						close(events[i].data.fd);

						break;
					}else{
						printf("%s\n", rbuf);
						send(events[i].data.fd, sbuf, sizeof(sbuf), 0);
					}

				}
			}

		}

		sleep(5);
		cnt++;
	}

	return 0;
}