I have had my slingbox classic for years and it has always worked fine. I have a linksys router that I enabled a port forward on and set a custom IP and port on the slingbox and everything worked as expected. I recently rebuilt my laptop and could no longer find the standalone client to download, only the browser plug-in version of the software.
I can watch on the LAN with no problems but no matter what I try the remote viewing does not work. I have tried my old IP (192.168.0.166) and port (5010) as well as the default values of 192.168.0.254:5001... My question is, how does the internet client know what IP to connect to? Let's say my cable modem is 188.8.131.52... that's the IP my client would need to know, not 192.168.0.254... but where does this get specified? I used to be able to tell the client to connect to 184.108.40.206:5010 and everything worked fine...
You would actually setup the firewall rules on your router to forward the UDP and TCP port to your Slingbox's private IP address. Once you have registered your Slingbox ID in your Sling Accounts (https://slingaccounts.slingmedia.com), the Sling Products Authentication and Registration Control System (sparcs.slingmedia.com) will keep track of the Slingbox's public IP address. It does this by registring information packets to the Sling Management Server (ms.sling.com). So, basically this is a Sling proprietary version of Dynamic Domain Name System (DDNS)
Btw, you can find out your public IP address by going to (http://www.canyouseeme.org/). If you use a computer that is on the same network as the Slingbox then that's its public IP address as well. Since all of your networked equipment in your private nework share the same public IP address. You can also test the port availablity from that website to see if your port fowarding rules for your Slingbox are working.
Also, you still can add a entry into your Slingbox Directory to use either the Slingbox ID or direct IP address to negotiate the connection. However, you'll need to use Slingbox Desktop to make a new entry.