A Web Server in C
I implemented a web server in C language using only the standard libraries and thought it would be useful for you guys if I share the code. The server runs on Linux and includes features like handling HTTP GET request, handling content types(txt, html, jpg, zip. rar, pdf, php etc.), sending proper HTTP error codes, serving the files from a web root, change in web root in a config file, zero copy optimization using sendfile method and php file handling. A port number should be provided as a command line argument. After the server is up and running you can request for files using a web browser like Firefox. For an example assume port number is "9000" and if you want to request a file called "test.php" which is in the webroot, use http://localhost:9000/test.php WebServer.c /* * 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 #include #include #include #include #include #include #include #include #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} }; /* 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 "conf" for reading FILE *in = fopen("conf", "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("Recieve 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, "index.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, ""); send_new(fd, "404 Not Found: The requested resource could not be found!"); //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; } } } 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, ""); send_new(fd, "415 Unsupported Media Type!"); } } 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 */ } Make sure you have installed php and there's exist a "conf" file consisted of the webroot before running this. Enjoy!
November 17, 2012
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