Trouble connecting two computers over the internet (TCP/IP)

I am trying to connect to my instance of sql server on my personal laptop using my lab computer. My laptop has no problem connecting to my lab pc from any network, however I cannot get the connection to go the other way around. When I ping my laptop from my lab computer using cmd>ping (laptop public ip address) the connection times out. However if I try the same command on my laptop, the ping command registers a response.

I have setup a static ip address for my laptop already, and it is the one I have been using to test the connection. What could possibly be blocking the connection?

My OS is windows 7.