C:HTTP webserver - the image "http://localhost.... cannot be displayed because it contains errors - html

Question

It's my first time dabbling with socket programming and I stumbled upon this amazing code from https://dzone.com/articles/web-server-c.
WHAT WE NEED TO DO: implement a simple HTTP web server that uses the web browser(input from the user) as a client
Here it is:
/*
* WebServer.c
*
* Created on: Nov 3, 2012
* Author: pavithra
*
* A web server in C language using only the standard libraries.
* The port number is passed as an argument.
*
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#define EOL "\r\n"
#define EOL_SIZE 2
typedef struct {
char *ext;
char *mediatype;
} extn;
//Possible media types
extn extensions[] ={
{"gif", "image/gif" },
{"txt", "text/plain" },
{"jpg", "image/jpg" },
{"jpeg","image/jpeg"},
{"png", "image/png" },
{"ico", "image/ico" },
{"zip", "image/zip" },
{"gz", "image/gz" },
{"tar", "image/tar" },
{"htm", "text/html" },
{"html","text/html" },
{"php", "text/html" },
{"pdf","application/pdf"},
{"zip","application/octet-stream"},
{"rar","application/octet-stream"},
{0,0} };
//find webroot, add design
/*
A helper function
*/
void error(const char *msg) {
perror(msg);
exit(1);
}
/*
A helper function
*/
int get_file_size(int fd) {
struct stat stat_struct;
if (fstat(fd, &stat_struct) == -1)
return (1);
return (int) stat_struct.st_size;
}
/*
A helper function
*/
void send_new(int fd, char *msg) {
int len = strlen(msg);
if (send(fd, msg, len, 0) == -1) {
printf("Error in send\n");
}
}
/*
This function recieves the buffer
until an "End of line(EOL)" byte is recieved
*/
int recv_new(int fd, char *buffer) {
char *p = buffer; // Use of a pointer to the buffer rather than dealing with the buffer directly
int eol_matched = 0; // Use to check whether the recieved byte is matched with the buffer byte or not
while (recv(fd, p, 1, 0) != 0) // Start receiving 1 byte at a time
{
if (*p == EOL[eol_matched]) // if the byte matches with the first eol byte that is '\r'
{
++eol_matched;
if (eol_matched == EOL_SIZE) // if both the bytes matches with the EOL
{
*(p + 1 - EOL_SIZE) = '\0'; // End the string
return (strlen(buffer)); // Return the bytes recieved
}
} else {
eol_matched = 0;
}
p++; // Increment the pointer to receive next byte
}
return (0);
}
/*
A helper function: Returns the
web root location.
*/
char* webroot() {
// open the file "kill.txt" for reading
FILE *in = fopen("kill.txt", "rt");
// read the first line from the file
char buff[1000];
fgets(buff, 1000, in);
// close the stream
fclose(in);
char* nl_ptr = strrchr(buff, '\n');
if (nl_ptr != NULL)
*nl_ptr = '\0';
return strdup(buff);
}
/*
Handles php requests
*/
void php_cgi(char* script_path, int fd) {
send_new(fd, "HTTP/1.1 200 OK\n Server: Web Server in C\n Connection: close\n");
dup2(fd, STDOUT_FILENO);
char script[500];
strcpy(script, "SCRIPT_FILENAME=");
strcat(script, script_path);
putenv("GATEWAY_INTERFACE=CGI/1.1");
putenv(script);
putenv("QUERY_STRING=");
putenv("REQUEST_METHOD=GET");
putenv("REDIRECT_STATUS=true");
putenv("SERVER_PROTOCOL=HTTP/1.1");
putenv("REMOTE_HOST=127.0.0.1");
execl("/usr/bin/php-cgi", "php-cgi", NULL);
}
/*
This function parses the HTTP requests,
arrange resource locations,
check for supported media types,
serves files in a web root,
sends the HTTP error codes.
*/
int connection(int fd) {
char request[500], resource[500], *ptr;
int fd1, length;
if (recv_new(fd, request) == 0) {
printf("Receive Failed\n");
}
printf("%s\n", request);
// Check for a valid browser request
ptr = strstr(request, " HTTP/");
if (ptr == NULL) {
printf("NOT HTTP !\n");
} else {
*ptr = 0;
ptr = NULL;
if (strncmp(request, "GET ", 4) == 0) {
ptr = request + 4;
}
if (ptr == NULL) {
printf("Unknown Request ! \n");
} else {
if (ptr[strlen(ptr) - 1] == '/') {
strcat(ptr, "test.html");
}
strcpy(resource, webroot());
strcat(resource, ptr);
char* s = strchr(ptr, '.');
int i;
for (i = 0; extensions[i].ext != NULL; i++) {
if (strcmp(s + 1, extensions[i].ext) == 0) {
fd1 = open(resource, O_RDONLY, 0);
printf("Opening \"%s\"\n", resource);
if (fd1 == -1) {
printf("404 File not found Error\n");
send_new(fd, "HTTP/1.1 404 Not Found\r\n");
send_new(fd, "Server : Web Server in C\r\n\r\n");
send_new(fd, "<html><head><title>404 Not Found</head></title>");
send_new(fd, "<body><p>404 Not Found: The requested resource could not be found!</p></body></html>\r\n");
//Handling php requests
} else if (strcmp(extensions[i].ext, "php") == 0) {
php_cgi(resource, fd);
sleep(1);
close(fd);
exit(1);
} else {
printf("200 OK, Content-Type: %s\n\n",
extensions[i].mediatype);
send_new(fd, "HTTP/1.1 200 OK\r\n");
send_new(fd, "Server : Web Server in C\r\n\r\n");
if (ptr == request + 4) // if it is a GET request
{
if ((length = get_file_size(fd1)) == -1)
printf("Error in getting size !\n");
size_t total_bytes_sent = 0;
ssize_t bytes_sent;
while (total_bytes_sent < length) {
//Zero copy optimization
if ((bytes_sent = sendfile(fd, fd1, 0,
length - total_bytes_sent)) <= 0) {
if (errno == EINTR || errno == EAGAIN) {
continue;
}
perror("sendfile");
return -1;
}
total_bytes_sent += bytes_sent;
}
//why is it not appearing up to 11:30
}
}
break;
}
int size = sizeof(extensions) / sizeof(extensions[0]);
if (i == size - 2) {
printf("415 Unsupported Media Type\n");
send_new(fd, "HTTP/1.1 415 Unsupported Media Type\r\n");
send_new(fd, "Server : Web Server in C\r\n\r\n");
send_new(fd, "<html><head><title>415 Unsupported Media Type</head></title>");
send_new(fd, "<body><p>415 Unsupported Media Type!</p></body></html>");
}
}
close(fd);
}
}
shutdown(fd, SHUT_RDWR);
}
int main(int argc, char *argv[]) {
int sockfd, newsockfd, portno, pid;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
if (argc < 2) {
fprintf(stderr, "ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd, 5);
clilen = sizeof(cli_addr);
/*
Server runs forever, forking off a separate
process for each connection.
*/
while (1) {
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");
pid = fork();
if (pid < 0)
error("ERROR on fork");
if (pid == 0) {
close(sockfd);
connection(newsockfd);
exit(0);
} else
close(newsockfd);
} /* end of while */
close(sockfd);
return 0; /* we never get here */
}
NOTE: the kill.txt contains the directory of the server, the files(jpegs, gifs, etc.: /home/user/Desktop)
PROBLEM:
1. After I compile the program and execute it on my web browser as "localhost:port number/file" this is what appears on my web browser:
the image "http://localhost.... cannot be displayed because it contains errors.
And this is what appears on my terminal:
GET /sample5.gif HTTP/1.1
Opening "/home/user/Desktop/sample5.gif"
200 OK, Content-Type: image/gif
GET /favicon.ico HTTP/1.1
Opening "/home/user/Desktop/favicon.ico"
404 File not found Error
How do I fix this? Any help/comment would be greatly appreciated! Thanks.
Where is that favicon.ico bit coming from? /I looked this up and apparently having that favicon.ico bit is quite normal (can somebody please confirm this?)/

Answer 1

… I stumbled upon this amazing code from …
It is indeed amazing how bad it is.
At the end of the function int connection(int fd) there's:
close(fd);
}
}
shutdown(fd, SHUT_RDWR);
}
Browsers don't like the connection being reset by peer (due to close()) before it's tidily shut down. Move the close() after the shutdown().
The program neglects to reap child processes, thus a zombie process remains after each request. #include <signal.h> and add sigignore(SIGCHLD); at the start of main().
If the action for the SIGCHLD signal is set to SIG_IGN, child
processes of the calling processes will not be transformed into zombie
processes when they terminate.