The server app is currently for Mac OS X 10.8 and above only, and you can get it either via the Mac App Store, or by downloading it directly. More info at http://theblockheads.net/server.html and direct download links:
Windows and Linux versions of the server are currently in development.
If you are setting up a server, and wish to invite people to join, please keep in mind that you need to give people your public IP address. If your IP starts with 192 then it is a local IP, and people won’t be able to access it from outside your local network, so you need to find out what your public IP is.
If you have a dynamic IP address (which is pretty common) you may need to use a service like www.noip.com to give you a url that will stay the same even when your IP address changes.
You may also need to change settings on your firewall or router, to set up port forwarding and allow connections on UDP Port 15151 to be directed to your Mac. Make sure you select UDP, TCP won’t work.
Once you get it up and running, you can share a url to your server with blockheads:// or http://theblockheads.net/join/ at the start, and when someone taps it from an iPhone or iPad with The Blockheads installed, it will automatically start the game and fill in the details.
Some examples would be:
and you can also add the port to the end:
(note none of these will actually work, they are just examples).