Re learning mode. A bit of play with epoll

epoll_test.c

/* 
 * Program to serve many client request without blocking 
 * using epoll 
 *
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <netinet/in.h> 


#define BUF_SIZE 500
#define MAX_EVENTS 10 

int
main(int argc, char *argv[])
{

	/* epoll specific */
	struct epoll_event ev ;  
	struct epoll_event  events[MAX_EVENTS] ; /* Store available events here */
	int nfds ;				 /* No of fds ready for IO */ 
	int epollfd ;  				 /* epoll instance fd */ 

	/* Socket specific declarations */
	int my_socket ;				/*Socket desc */ 
	struct sockaddr_in in_name ;    	/* holds the sa_family, etc.. */ 
	socklen_t in_name_len ;         /* socket length */
        unsigned short port = 12345;    /* Location */ 
	int bind_ret ; 			/* Bind() RC */
	int bck_log = 5 ; 		/* Max pending connections in sockfd */ 
	int listen_sock ;			 
	int conn_sock;		/* Accpeted connection desc */ 
	int n = 0 ; 		/* Loop var */
	/* Create a socket, bind and listen */ 

	my_socket = socket(AF_INET, SOCK_STREAM, 0) ; 

	if (my_socket == -1 ) { 
		printf("socket error\n");
		exit(1);
	} 

	/* Define the name */ 
	/* Check if sizeof on this gives us the right bytes */
	memset(&in_name, 0 , sizeof(&in_name)) ; 

	in_name.sin_family = AF_INET;  
	in_name.sin_port = htons(port); 
	in_name.sin_addr.s_addr = INADDR_ANY ; 

	in_name_len = sizeof(struct sockaddr_in); 

	/* Bind the socket */ 
	bind_ret = bind(my_socket, (struct sockaddr *) &in_name, in_name_len);
	if (bind_ret == -1) { 
		printf("Bind error\n");
		close(my_socket); 
		exit(1);
	}
	/* Listen */ 

	printf("Listening to incoming requests\n");
	fflush(stdout); 
	listen_sock = listen( my_socket, bck_log);
	if (listen_sock) {
		printf("listen error\n");
		close(my_socket);
		exit(1);
	}

	/* Setup an epoll instance */ 
	epollfd = epoll_create(10);
	if (epollfd == -1) {
		perror("epoll_create");
		exit(EXIT_FAILURE);
	}
	listen_sock = my_socket ; 

	/* Set the events to read */
         ev.events = EPOLLIN;  		/* Set it for read operations */
         ev.data.fd = listen_sock; 	/* Our listener name */ 
	
	/* Register the target fd to the ep and associate event with the ep */
        if (epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {
         	perror("epoll_ctl: listen_sock");
         	exit(EXIT_FAILURE);
        }

	/* Loop forever */ 
	for (;;) { 

	 /* Wait for I/O event on the epfd */ 
		nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1 ); 
		if (nfds == -1) {
		    perror("epoll_pwait");
		    exit(EXIT_FAILURE);
		}
		printf("No of nfds %d \n ", nfds );
		fflush(stdout); 
		/* After timeout we have the ready count of descriptors */ 
		/* Loop thru the I/O ready descriptors */
		for (n = 0; n < nfds; ++n) {
		   /*Find the one we were listening */ 
		   /* This is found from the event data fd that we set using epoll_ctl earlier */ 
                   if (events[n].data.fd == listen_sock) {
		       /* If this is our incoming connection*/
		       /* Accept the connection */ 
                       conn_sock = accept(my_socket, (struct sockaddr *) &in_name, &in_name_len);

		       printf(" Listen event events[%d].data.fd : %d \n", n, events[n].data.fd ) ; 	
                       if (conn_sock == -1) {
                           perror("accept");
                           exit(EXIT_FAILURE);
                       }
		       //setnonblocking(conn_sock); 
		       printf("non blocking goes here \n");
		       /* Set the events that we want to handle */
		       ev.events = EPOLLIN | EPOLLET ; 
		       ev.data.fd = conn_sock ; 
		       /* Add it to our event list, service it when ready */ 
		       if ( epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock, &ev) == -1 ) {
				perror("epoll ctl : conn_sock " ); 
				exit(EXIT_FAILURE); 
		       }
		   }
	           else { 
			/* If any other in the event list */ 
			/* Check the fd in the event struct and take action */  	
		        printf("This is the event that is not from listen connection \n"); 	
			printf("events[%d].data.fd : %d \n", n, events[n].data.fd ) ; 	

  
			} 
		}
	} 
}