http_server.cpp

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

#define BACKLOG 10 // max concurrent connections
#define MAX_DATA_SIZE 100 // receive message buffer size
#define FILE_READ_SIZE 512 // send file chunk size
#define HTTP_200 "HTTP/1.1 200 OK"
#define HTTP_400 "HTTP/1.1 400 Bad Request"
#define HTTP_404 "HTTP/1.1 404 Not Found"

using namespace std;

int main(int argc, char const *argv[]) {
	int pid;
	// int yes = 1; // setsockopt variable
	int bytes_received;
	char rec_buf[MAX_DATA_SIZE]; // receive buffer
	char file_buf[FILE_READ_SIZE]; // file buffer
	int file_block_size; // read file block size 
	int socket_fd, new_fd; // listen on socket_fd, serve connections on new_fd
	struct addrinfo hints;
	struct addrinfo *serv_info;  // will point to the results
	struct sockaddr_storage their_addr; // connector's address information
	socklen_t their_addr_size; // connector's address size
	FILE *file_to_send; // file requested by client
	string request; // request string
	char* file_name; // file name to send
	const string get ("GET"); // get string

	if(argc != 3) {
		cout << "usage: html_sever port root_dir\n";
		return 1;
	}

	// initialize hints struct
	memset(&hints, 0, sizeof(hints)); // make sure the struct is empty
	hints.ai_family = AF_UNSPEC;     // don't care IPv4 or IPv6
	hints.ai_socktype = SOCK_STREAM; // TCP stream sockets
	hints.ai_flags = AI_PASSIVE;     // fill in my IP for me

	// getaddrinfo
	// TODO: change cout to gai_strerror
	if(getaddrinfo(NULL, argv[1], &hints, &serv_info) != 0) { // if unsuccessful
		cout << "getaddrinfo error"; // print error
		return 1; 
	}

	// create socket
	socket_fd = socket(serv_info->ai_family, serv_info->ai_socktype, serv_info->ai_protocol); // open socket
	
	// TODO: add setsockopt (reuse ports)

	// bind socket
	if(bind(socket_fd, serv_info->ai_addr, serv_info->ai_addrlen) == -1) { // if binding failed
		cout << "bind error"; // print error
		return 1;
	}

	// cleanup
	freeaddrinfo(serv_info);

	// listen on socket
	if(listen(socket_fd, BACKLOG) == -1) { // if unsuccessful
		cout << "listen error"; // print error
		return 1;
	}

	// TODO: clear zombies
	
	while(1) { // accept loop
		their_addr_size = sizeof(their_addr);
		new_fd = accept(socket_fd, (struct sockaddr*)&their_addr, &their_addr_size); // accept connection
		if(new_fd == -1) { // if unsuccessful
			cout << "accept error"; // print error
			continue;
		}

		if((pid = fork()) < 0) // if unsuccessful
			cout << "fork error"; // print error
		else if(pid == 0) { // child process
			close(socket_fd); // close listener

			// TODO: refactor to functions

			if((bytes_received = recv(new_fd, rec_buf, MAX_DATA_SIZE - 1, 0)) == -1) { // receive request
				send(new_fd, HTTP_400, strlen(HTTP_400), 0); // send http400
				cout << "receive error"; // print error
				exit(1); // terminate child (error)
			}
			rec_buf[MAX_DATA_SIZE] = '\0'; // close array
			request = rec_buf; // convert char array to string
			if(!(request.compare(0, 3, get))) { // if received GET request
				// get file name (second rec_buf argument)
				file_name = strtok(rec_buf, " ");
				file_name = strtok(NULL, " ");
				// TODO: prepend argv[2] to file_name
				file_to_send = fopen(file_name, "r"); // open file to send (read-only)
				if(file_to_send == NULL) { // if file not found
					send(new_fd, HTTP_404, strlen(HTTP_404), 0); // send http404
					cout << "file not found error"; // print error
					exit(1); // terminate child (error)
				} else {
					send(new_fd, HTTP_200, strlen(HTTP_200), 0); // send http200
					bzero(file_buf, FILE_READ_SIZE); // zero file buffer
					while((file_block_size = fread(file_buf, sizeof(char), FILE_READ_SIZE, file_to_send)) > 0) {
						if(send(new_fd, file_buf, file_block_size, 0) < 0) {
							cout << "send file error"; // print error
							exit(1); // terminate child (error)
						}
						bzero(file_buf, FILE_READ_SIZE); // clear buffer for new iteration
					}
					fclose(file_to_send); // close open file
				}
			} else {
				send(new_fd, HTTP_400, strlen(HTTP_400), 0); // send http400
				cout << "received data error"; // print error
				exit(1); // terminate child (error)
			}
			close(new_fd); // close socket
			exit(0); // terminate child (no-error)
		}
		close(new_fd); // close new connection on parent
	}

	return 0;
}