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#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
/*
#include <netinet/in.h>
struct sockaddr_in {
   short   sin_family;
   u_short sin_port;
   struct  in_addr sin_addr;
   char    sin_zero[8];
};


struct in_addr {
   u_long s_addr;  // load with inet_aton()
};
*/
int create_tcp_socket();
char *get_ip(char *host);
char *build_get_query(char *host, char *page);
void usage();

#define HOST "www.umsl.edu"
#define PAGE "/"
#define PORT 80
#define USERAGENT "Mozilla/5.0"
int main(int argc, char **argv)
{
    struct sockaddr_in *remote;
    int sock;
    int tmpres;
    char *ip;
    char *get;
    char buf[BUFSIZ+1];
    char *host;
    char *page;

    if (argc == 1) {
        usage();
        exit(2);
    }
    host = argv[1];
    if (argc > 2) {
        page = argv[2];
    } else {
        page = PAGE;
    }
    sock = create_tcp_socket();
    ip = get_ip(host);
    fprintf(stderr, "IP is %s\n", ip);
    remote = (struct sockaddr_in *)malloc(sizeof(struct sockaddr_in *));
    remote->sin_family = AF_INET;
    tmpres = inet_pton(AF_INET, ip, (void *)(&(remote->sin_addr.s_addr)));
    if ( tmpres < 0) {
        perror("Can't set remote->sin_addr.s_addr");
        exit(1);
    } else if (tmpres == 0) {
        fprintf(stderr, "%s is not a valid IP address\n", ip);
        exit(1);
    }
    remote->sin_port = htons(PORT);

    if (connect(sock, (struct sockaddr *)remote, sizeof(struct sockaddr)) < 0) {
        perror("Could not connect");
        exit(1);
    }
    get = build_get_query(host, page);
    fprintf(stderr, "Query is:\n<<START>>\n%s<<END>>\n", get);

    //Send the query to the server
    int sent = 0;
    while (sent < strlen(get)) {
        tmpres = send(sock, get+sent, strlen(get)-sent, 0);
        if (tmpres == -1) {
            perror("Can't send query");
            exit(1);
        }
        sent += tmpres;
    }
    //now it is time to receive the page
    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");
    }
    free(get);
    free(remote);
    free(ip);
    if ( close(sock)!=0)
        return -1;
    else
        return 0;
}

void usage()
{
    fprintf(stderr, "USAGE: htmlget host [page]\n\
    \thost: the website hostname. ex: coding.debuntu.org\n\
    \tpage: the page to retrieve. ex: index.html, default: /\n");
}


int create_tcp_socket()
{
    int sock;
    if ((sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
        perror("Can't create TCP socket");
        exit(1);
    }
    return sock;
}


char *get_ip(char *host)
{
    struct hostent *hent;
    int iplen = 15; //XXX.XXX.XXX.XXX
    char *ip = (char *)malloc(iplen+1);
    memset(ip, 0, iplen+1);
    if ((hent = gethostbyname(host)) == NULL) {
        herror("Can't get IP");
        exit(1);
    }
    if (inet_ntop(AF_INET, (void *)hent->h_addr_list[0], ip, iplen) == NULL) {
        perror("Can't resolve host");
        exit(1);
    }
    return ip;
}

char *build_get_query(char *host, char *page)
{
    char *query;
    char *getpage = page;
    char *tpl = "GET /%s HTTP/1.0\r\nHost: %s\r\nUser-Agent: %s\r\n\r\n";
    if (getpage[0] == '/') {
        getpage = getpage + 1;
        fprintf(stderr,"Removing leading \"/\", converting %s to %s\n", page, getpage);
    }
    // -5 is to consider the %s %s %s in tpl and the ending \0
    query = (char *)malloc(strlen(host)+strlen(getpage)+strlen(USERAGENT)+strlen(tpl)-5);
    sprintf(query, tpl, getpage, host, USERAGENT);
    return query;
}

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