Understanding Internet Security - Implementing SSL/TLS Using Cryptography and PKI - page 9

HTTP/1.0 or HTTP/1.1 depending on which version of the HTTP protocol the
client understands.
NOTE At the time of this writing, there are only two versions of HTTP; the
differences are immaterial to this topic.
The GET command itself is followed by a carriage-return/line-feed pair (0x0A
0x0D) and a colon-separated, CRLF-delimited list of headers that describe how
the client wants the response to be returned. Only one header is required — the
Host header, which is required to support virtual hosting , the situation where
several hosts share one IP address or vice-versa. The Connection header is not
required, but in general you should send it to indicate to the client whether you
want it to Keep-Alive the connection — if you plan on requesting more docu-
ments on this same socket — or Close it. If you omit the Connection: Close
header line, the server keeps the socket open until the client closes it. If you're
just sending a single request and getting back a single response, it's easier to
let the server just close the connection when it's done sending. The header list
is terminated by an empty CRLF pair.
A minimal HTTP GET command looks like this:
GET /index.html HTTP/1.1
Host: www.server.com
Connection: close
The code to format and submit a GET command over an established socket is
shown in Listing 1-6. Note that the input is the socket itself — the connection
argument — the path of the document being requested, and the host (to build
the host header).
Listing 1-6: “http.c” http_get
#define MAX_GET_COMMAND 255
/**
* Format and send an HTTP get command. The return value will be 0
* on success, -1 on failure, with errno set appropriately. The caller
* must then retrieve the response.
*/
int http_get( int connection, const char *path, const char *host )
{
static char get_command[ MAX_GET_COMMAND ];
sprintf( get_command, “GET /%s HTTP/1.1\r\n”, path );
if ( send( connection, get_command, strlen( get_command ), 0 ) == -1 )
{
return -1;
}
sprintf( get_command, “Host: %s\r\n”, host );
if ( send( connection, get_command, strlen( get_command ), 0 ) == -1 )
{