How to shortcut execute php script without filling out form?

Ok so there is a website that has two input boxes inside a POST form
that uses the action="rcon.php"


here is the code for the form

<form method=POST action="/rcon.php">
<input size=25 type=text class="sm" name="addr">
<input size=20 type=text class="sm" name="rcon">
<input class="coolbuttonblue" type=submit value="Submit">
<input class="coolbutton" type=checkbox name="announceflag" value="1"
checked>

What I want to do is to be able to execute this script without having
to fill out the form every time. My ideal thought was to make a
shortcut to the URL http://whateversite.com/rcon.php?addr=someaddress&rcon=somercon&announceflag=1
and that way everytime i click the shortcut, it executes the script,
and passes it static data that I put in the shortcut, therefor I don't
have to fill out a form every time and click submit.

This is not my website I am dealing with, it is a public site that
uses a form that has the code above. So why can't I just pass the
data through the address bar? Is there some security in place that
might prevent url passing of variables?

If I can't do that, would writing a script that uses sockets be able
to accomplish this somehow? Or is it somehow not possible without
using their html form

.