(buf is a char array with the contents of the http data, pLength is a char *)
pLength = strstr(buf, lenTok);
//advance pointer past "Content-Length: " to point to data
if (pLength != NULL)
    pLength = (pLength + 16);
int length = 0;
for (int i = 0; i < /*length of Content-Length:*/; i++)
{
    length = length * 10;
    length = length + (pLength[i] - '0');
}