Sling Media has made quite a few changes in the last year on how their Sling Player program and SlingBox firmware works in order to eliminate remote viewing problems. The way they have done this is great but at times it can get very confusing.
In order to help you understand what changes they have made and why some people are confused about the port forwarding problems let’s start at the beginning.
Originally in order to connect to your SlingBox remotely you had to have a TCP port forwarded to your SlingBox in your routers configuration setup. This was the only way you could connect remotely to your SlingBox.
So let’s start with what an open TCP port is and does.
Without going into tons of details of how and what TCP port forwarding does here is a simple explanation.
You have your home network setup with several different things connected to it. Each one of them are given a specific network address. Not anyone of them can use the same address as the other. For example the network address of your computer might be 192.168.1.100 and the network address of your Slingbox might be 192.168.1.237.
A TCP port forward is a doorway to your Slingbox. The way it works is that you “open” up this port in your router settings. Then when you are Slinging remotely your SlingPlayer says something like this, in lay man terms, to your router. “Hey I want to connect to the Slingbox at “192.168.1.237” and go through this doorway, a specific port number, to get there.
Your router then checks to see if that doorway, port forward, is open to your Slingbox. If it is then it sends the info to it. If not open then it says nope can’t go there and stops everything.
So if you don’t have a TCP port forwarded, a doorway, to your Slingbox then you will be able to reach it.
UDP works completely different.
UDP can tell your router where to send something to. Inside the information packet that it is sending to your home router it also has the place to send the info to in your LAN.
But of course your router needs to know where your Slingbox is. So your Slingbox sends out to the Sling Media servers where it is at in your LAN and your WAN.
Let’s say your Slingbox is at 192.168.1.237 on your LAN (at home) and 126.96.36.199 on the Internet (WAN). It tells the Sling Media service this is it’s private home address and here is the public internet address.
Then try to connect to your Slingbox via UDP it sends this info to your router. It tells the router to send this packet of info straight to 192.168.1.237 regardless of what resides at that address. The router doesn’t care it just sends it there without any error checking at all.
That is why you don’t need a port forward setup for the Slingbox and UDP.
How this relates to Slinging
When you setup your SlingBox it tries to setup a TCP port forward for you. If it or you can’t set one up it will drop back to using UDP to Sling remotely.
The only problem with that your can’t use UDP for everything. It works with the Web SlingPlayer app, both Mac and Windows stand alone programs and I am told also for the iPhone and Blackberry.
I have no way to test the iPhone but have tested UDP usage for the Blackberry and it did not work for me. It also won’t work for the SlingCatcher, Windows Mobile player and Palm Symbian programs.
Ever wonder why someone said “Hey how come my SlingPlayer for Windows works fine remotely but my Catcher doesn’t?” That is because he is using UDP for Windows and there is no proper TCP port forwarded to the SlingBox so the Catcher won’t connect.
This can at times make it very hard to diagnose a remote connection problem. Someone could have a problem using UDP and all he needs to do is open up a TCP port and it goes away. It could also happen in the opposite. Someone having a TCP Slinging issue could try running UDP and see if it helps.
In this case here it resolved his issue completely
That’s the basics of UDP and TCP port forwarding for the Slingbox. If you have any questions regarding this let us know.
In depth resources.