So there are two ways you can do this:
1. The simple way (BOOOOH)
2. The harder way (:DDDD)
The difference is that the harder one lets you have your commands with the key " # ".
They both are the same.
Harder Version:
Step 1. Download Port Map:
http://www.macupdate.com/app/mac/27342/port-map/Step 2. Download the Source Code From This Forum Post
Step 3. Start Up Port Map. Click the + and in Local + Desired Port Type 28785. Make sure that TCP and UDP are checked. Then set your descripiton and click Add Mapping. Repeat this with 28786.
Step 4. Download Caffeine: lightheadsw.com/caffeine/
Step 5. Run Caffeine and click it so that your computer will not go to sleep
Step 6. Open Terminal.
Step 7. Type into Terminal "cd " and then drag the folder which is the downloaded source code. If it worked it should say something like (If the downloaded source code is in Downloads) . Then press enter.
cd /Users/Username/Downloads/Source_Code
Step 8. Now type " ./remod " and press enter
Step 9. Done!

Here is the source code (attached). In the next reply I will show you how to make a simple one for your personal use.
EDIT: THE SOURCE CODE IS A LINK: DOWNLOAD THAT, IT WAS TOO BIG TO ATTACH (25 MB)
~Hosted on MediaFire~
LINK FOR SOURCE CODE:
http://www.mediafire.com/?l0xi28k2ng41wh8