Poll Server

poll_server.c

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

#define PORT 8080
#define MAX_EVENTS 256

#define HELLO_RESPONSE "HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: 14\r\n\r\nHello, World!\n"

int set_nonblocking(int fd) {
	int flags = fcntl(fd, F_GETFL, 0);
	if (flags == -1) {
		perror("Error in fcntl F_GETFL");
		return 1;
	}

	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
		perror("Error in fcntl F_SETFL");
		return 1;
	}

	return 0;
}

int main() {
	int server_socket = socket(AF_INET, SOCK_STREAM, 0);
	if (server_socket == -1) {
		perror("socket");
		return 1;
	}

	int enable_reuse = 1;
	if (setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, &enable_reuse, sizeof(int)) == -1) {
		perror("Error in setsockopt");
		return 1;
	}

	if (set_nonblocking(server_socket)) {
		perror("Error in set_nonblocking");
		return 1;
	}

	struct sockaddr_in server_addr;
	server_addr.sin_family = AF_INET;
	server_addr.sin_addr.s_addr = INADDR_ANY;
	server_addr.sin_port = htons(PORT);

	if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
		perror("bind");
		return 1;
	}

	if (listen(server_socket, MAX_EVENTS) == -1) {
		perror("listen");
		return 1;
	}

	printf("Server is listening on port %d...\n", PORT);

	int epoll_fd = epoll_create1(0);
	if (epoll_fd == -1) {
		perror("Error in epoll_create1");
		return 1;
	}
	struct epoll_event event;
	event.events = EPOLLIN | EPOLLET;
	event.data.fd = server_socket;
	struct epoll_event epoll_events[MAX_EVENTS];

	if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_socket, &event) == -1) {
		perror("Error in epoll_ctl");
		return 1;
	}

	char* buffer = malloc(sizeof(char) * 256);

	while (1) {
		int events = epoll_wait(epoll_fd, epoll_events, MAX_EVENTS, -1);
		for (int i = 0; i < events; i++) {
			if (epoll_events[i].data.fd == server_socket) {
				int client_socket = accept(server_socket, NULL, NULL);
				if (client_socket == -1) {
					perror("Error in accept");
					return 1;
				} else {
					if (set_nonblocking(client_socket)) {
						perror("Error in set_nonblocking");
						return 1;
					}

					event.data.fd = client_socket;
					event.events = EPOLLIN | EPOLLET;

					if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_socket, &event) == -1) {
						perror("Error in epoll_ctl");
						return 1;
					}
				}
			} else {
				int client_socket = epoll_events[i].data.fd;
				int bytes_received = recv(client_socket, buffer, 256, 0);

				if (bytes_received <= 0) {
					epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_socket, NULL);
					close(client_socket);
				} else {
					sendto(client_socket, HELLO_RESPONSE, sizeof(HELLO_RESPONSE), 0, NULL, 0);
				}
			}
		}
	}

	free(buffer);
	close(server_socket);
	close(epoll_fd);

	return 0;
}