epoll_echo_server.c

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

#define BACKLOG 512
#define MAX_EVENTS 128
#define MAX_MESSAGE_LEN 2048

void error(char* msg);


int main(int argc, char *argv[])
{
    if (argc < 2) {
        printf("Please give a port number: ./epoll_echo_server [port]\n");
        exit(0);
    } 

	// some variables we need
	int portno = strtol(argv[1], NULL, 10);
	struct sockaddr_in server_addr, client_addr;
	socklen_t client_len = sizeof(client_addr);

	char buffer[MAX_MESSAGE_LEN];
	memset(buffer, 0, sizeof(buffer));


	// setup socket
	int sock_listen_fd = socket(AF_INET, SOCK_STREAM, 0);
	if (sock_listen_fd < 0) {
		error("Error creating socket..\n");
	}

	memset((char *)&server_addr, 0, sizeof(server_addr));
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(portno);
	server_addr.sin_addr.s_addr = INADDR_ANY;
	

	// bind socket and listen for connections
	if (bind(sock_listen_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
		error("Error binding socket..\n");

	if (listen(sock_listen_fd, BACKLOG) < 0) {
        error("Error listening..\n");
    }
	printf("epoll echo server listening for connections on port: %d\n", portno);


	struct epoll_event ev, events[MAX_EVENTS];
	int new_events, sock_conn_fd, epollfd;
	
	epollfd = epoll_create(MAX_EVENTS);
	if (epollfd < 0)
	{
		error("Error creating epoll..\n");
	}
	ev.events = EPOLLIN;
	ev.data.fd = sock_listen_fd;

	if (epoll_ctl(epollfd, EPOLL_CTL_ADD, sock_listen_fd, &ev) == -1)
	{
		error("Error adding new listeding socket to epoll..\n");
	}

	while(1)
	{
		new_events = epoll_wait(epollfd, events, MAX_EVENTS, -1);
		
		if (new_events == -1)
		{
			error("Error in epoll_wait..\n");
		}

		for (int i = 0; i < new_events; ++i)
		{
			if (events[i].data.fd == sock_listen_fd)
			{
				sock_conn_fd = accept4(sock_listen_fd, (struct sockaddr *)&client_addr, &client_len, SOCK_NONBLOCK);
				if (sock_conn_fd == -1)
				{
					error("Error accepting new connection..\n");
				}

				ev.events = EPOLLIN | EPOLLET;
				ev.data.fd = sock_conn_fd;
				if (epoll_ctl(epollfd, EPOLL_CTL_ADD, sock_conn_fd, &ev) == -1)
				{
					error("Error adding new event to epoll..\n");
				}
			}
			else
			{
				int newsockfd = events[i].data.fd;
				int bytes_received = recv(newsockfd, buffer, MAX_MESSAGE_LEN, 0);
				if (bytes_received <= 0)
				{
					epoll_ctl(epollfd, EPOLL_CTL_DEL, newsockfd, NULL);
					shutdown(newsockfd, SHUT_RDWR);
				}
				else
				{
					send(newsockfd, buffer, bytes_received, 0);
				}
			}
		}
	}
}



void error(char* msg)
{
	perror(msg);
	printf("erreur...\n");
	exit(1);
}