I think of server as remote server.
There is a significant difference between
"GET / send_data.php?latitude = "
and
"GET /send_data.php?latitude="
unless your server os allows filenames to begin with a space, which is foreign to me 
The Host address can be on your home network, I think (i.e. 192.168.xxx.xxx), but it should not be the router, is that what you're asking?
Also maybe you can post send_data.php?