Linux_Lab_41

Linux_Lab_41

//  Linux_Lab_41
//
//  Created by Sergiy on 28.01.17.

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

#define HOST "www.google.com.ua"
#define PAGE "/"
#define PORT 80

int createTCPsocket();
char *getIP(char *host);

int main(int argc, const char * argv[])
{
    char *my_URL;
    char *tokenPage;
    size_t length_URL_without_page;
    char *my_URL_without_page;
    char *tokenPort;
    size_t length_URL_without_page_and_port;
    char *my_URL_without_page_and_port;
    char *host;
    char *port_text;
    char *port_text_temp;
    char *page;
    int port;
    char *query;
    char *queryTemplate;
    int sock;
    char *ip;
    struct sockaddr_in *server;
    int tmpres;
    char buf[BUFSIZ+1];
    
    // Build query -START-
    
    if (argc == 1)
    {
        printf("For usage you have to provide URL (for example: www.gu.net:8101/leased_r.html)\n");
        exit(2);
    }
    
    my_URL = argv[1];
    //my_URL = "www.google.com";
    //my_URL = "www.linux.die.net/man/3/strchr";
    printf("The URL is %s\n", my_URL);
    
    // Take page from URL -START-
    
    tokenPage = strchr(my_URL, '/');
    
    if (tokenPage == NULL)
    {
        printf("There is no path provided.\n");
        page = "/";
        printf("Default path is %s\n", page);
    }
    else
    {
        page = malloc(strlen(tokenPage));
        memcpy(page, tokenPage, strlen(tokenPage));
    }
    
    printf("The page is %s\n", page);
    
    // Take page from URL -END-
    
    //----------------
    
    // define URL without page -START-
    
    if (tokenPage == NULL)
    {
        my_URL_without_page = malloc(strlen(my_URL));
        memcpy(my_URL_without_page, my_URL, strlen(my_URL));
    }
    else
    {
        length_URL_without_page = strlen(my_URL) - strlen(tokenPage);
        my_URL_without_page = malloc(length_URL_without_page);
        memcpy(my_URL_without_page, my_URL, length_URL_without_page);
    }
    
    //printf("URL without page is %s\n", my_URL_without_page);
    
    // define URL without page -END-
    
    //-------------
    
    // take port_text from URL -START-
    
    tokenPort = strchr(my_URL_without_page, ':');
    
    if (tokenPort == NULL)
    {
        printf("There is no port provided.\n");
        port_text = "";
        port = 80;
        printf("Default port is %d\n", port);
    }
    else
    {
        port_text = malloc(strlen(tokenPort));
        memcpy(port_text, tokenPort, strlen(tokenPort));
        //get port from port_text
        port_text_temp = port_text +1;
        port = atoi(port_text_temp);
        printf("The port is %d\n", port);
    }
    
    printf("The port(text) is %s\n", port_text);
    
    // take port_text from URL -END-
    
    //-------------
    
    // define URL without port -START-
    
    if (tokenPort == NULL)
    {
        my_URL_without_page_and_port = malloc(strlen(my_URL_without_page));
        memcpy(my_URL_without_page_and_port, my_URL_without_page, strlen(my_URL_without_page));
    }
    else
    {
        length_URL_without_page_and_port = strlen(my_URL_without_page) - strlen(tokenPort);
        my_URL_without_page_and_port = malloc(length_URL_without_page_and_port);
        memcpy(my_URL_without_page_and_port, my_URL_without_page, length_URL_without_page_and_port);
    }
    
    //printf("URL without page and port is %s\n", my_URL_without_page_and_port);
    
    // define URL without port -END-
    
    //-------------
    
    // take host from URL -START-
    
    host = my_URL_without_page_and_port;
    printf("host is %s\n", host);
    
    // take host from URL -END-
    
    //-------------
    
    queryTemplate = "GET %s HTTP/1.1\r\nHost: %s%s\r\n\r\n";
    query = (char *)malloc(strlen(queryTemplate) + strlen(page) + strlen(host) + strlen(port_text) - 5);
    sprintf(query, queryTemplate, page, host, port_text);
    fprintf(stderr, "Query is:\n<<START>>\n\n%s<<END>>\n", query);
     
    // Build query -END-
    
    //-----------
    
    // Create socket -START-
    
    sock = createTCPsocket();
    //printf("File descriptor that refers to endpoint is %d\n\n", sock);
    
    // Create socket -END-
    
    //-----------
    
    // Get IP -START-
    
    ip = getIP(host);
    
    fprintf(stderr, "IP is %s\n", ip);
    
    // Get IP -END-
    
    //---------
    
    // Setup server -START-
    
    server = (struct sockaddr_in *)malloc(sizeof(struct sockaddr_in *)) ;
    
    server->sin_family = AF_INET;
    //server->sin_addr.s_addr = INADDR_ANY;
    server->sin_port = htons(port);
    
    tmpres = inet_pton(AF_INET, ip, (void *)(&(server->sin_addr.s_addr)));
    
    if (tmpres < 0)
    {
        perror("Can't set remote->sin_addr.s_addr");
        exit(1);
    }
    else if (tmpres == 0)
    {
        fprintf("%s is not a valid IP address\n", ip);
        exit(1);
    }
    
    // Setup server -END-
    
    //-----------
    
    // Connect -START-
    
    if (connect(sock, (struct sockaddr *)server, sizeof(struct sockaddr)) < 0)
    {
        perror("Could not connect");
        exit(1);
    }
    
    // Connect -END-
    
    //-----------
    
    // Send the query to the server -START-
    
    int sent = 0;
    while (sent < strlen(query))
    {
        tmpres = send(sock, query+sent, strlen(query) - sent, 0);
        if (tmpres == -1)
        {
            perror("Can't send query");
            exit(1);
        }
        sent += tmpres;
    }
    
    // Send the query to the server -END-
    
    
    //receive the page -START-
    
    memset(buf, 0, sizeof(buf));
    
    int htmlstart = 0;
    
    char *htmlcontent;
    
    while ((tmpres = recv(sock, buf, BUFSIZ, 0)) > 0)
    {
        if (htmlstart == 0)
        {
            // under certain conditions this will not work.
            // If the \r\n\r\n part is splitted into two messages
            // it will fail to detect the beginning of HTML content
            
            htmlcontent = strstr(buf, "\r\n\r\n");
            if (htmlcontent != NULL)
            {
                htmlstart = 1;
                htmlcontent += 4;
            }
        }
        else
        {
            htmlcontent = buf;
        }
        if (htmlstart)
        {
            fprintf(stdout, htmlcontent);
        }
        
        memset(buf, 0, tmpres);
    }
    
    if (tmpres < 0)
    {
        perror("Error receiving data");
    }
    
    //receive the page -END-
    
    //------------
    
    //free(page);
    //free(my_URL_without_page);
    free(query);
    free(server);
    free(ip);
    close(sock);
    
    return 0;
}


int createTCPsocket()
{
    int sock;
    
    sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (sock < 0 )
    {
        perror("Failed to create socket\n");
        exit(1);
    }
    
    return sock;
}

char *getIP(char *host)
{
    struct hostent *hent;
    
    int iplen = 15; //XXX.XXX.XXX.XXX
    
    char *ip = (char *)malloc(iplen + 1);
    memset(ip, 0, iplen+1);
    
    char *host_without_www = host + 4;
    //printf("\nHost without www is %s\n", host_without_www);
    
    if ((hent = gethostbyname(host_without_www)) == NULL)
    {
        perror("Can't get IP\n");
        exit(1);
    }
    
    if ((inet_ntop(AF_INET, (void *)hent->h_addr_list[0], ip, iplen)) == NULL)
    {
        perror("\nCan't resolve host\n");
        printf("\n");
        exit(1);
    }
    
    return ip;
}