I cant get screen sharing to work on my home network

Question

I am trying to connect my macbook pro to screen sharing so i can access it at my school computers, which are all iMacs running 10.6.6. When i was at school, and connected to the wireless network at my school i could screen sharing through the finder>go>connect to server. Once screen sharing was enabled i just entered the vnc address and it connected flawlessly. When i got home, and i set my netgear router( wireless-n 150 model: wnr100v2) for port forwarding start port: 5900 end port:5900 server name vnc, and set the ip address to my computer, and when i tried to screen share from another macbook within my network through the finder>go>connect to server, i could not connect. Oddly when i connected my mobile me, i cold screen share over the network. I want to do a WAN screen sharing and i cannot figure out how do do it. I would appreciate any help because it is very important that i enable this feature.

Answer 1

I'm a little confused by your explanation (it's late), so I am going to say what I think I read:
You want to set up your home computer so you can access it via screen sharing from school.
The home computer needs sys prefs sharing screen sharing enabled, and sys prefs security firewall must allow it, too. You port forward port 5900 through your home router to that home computer, which may or may not require that you use a static "192.168.x.x" (or "10.x.x.x" -- whatever the router's LAN subnet is) LAN IP address on that computer -- some routers require that computers acting as servers have static IPAs -- some routers don't.
You need to find out what is the public (internet-facing) WAN IP address that your ISP has assigned to your router; it is not the 192.168.x.x (or 10.x.x.x) address given to your home computer by your home router. You can find that by going to http://checkip.dyndns.com on your home computer. Unless you pay extra for a static public IP address from your ISP, ISPs may (and do) change it periodically on you without warning. So vnc://123.45.67.89 may work one day but not the next.
Some routers have a built-in feature to work around this by allowing the router to advise dynamic DNS servers of any changes in the public-facing IP address of the router. Of course, you need to have established an account with a dynamic DNS provider so you have a host name (like lomberg.noip.com or lomberg.dyndns.com). These are generally free accounts unless you want a special name that doesn't have the dynamic DNS provider as part of your host name.
If your router does not have this capability, these dynamic DNS providers have a piece of software that you will need to install on your home computer (the "VNC server") that reports changes in your public-facing IP address to their DNS servers.
Once this is done, then from afar, you can ⌘k to vnc://lomberg.dyndns.com (or whatever you set up your host name to be with dyndns or equivalent outfit) and you don't need to worry about what your ISP has done to you with regards to your public-facing WAN IP address du jour.
Note that with some (most?) routers, when you are on your home network, you will not be able to vnc to the host name or numeric WAN IPA in this manner. I don't know why it doesn't work, it just doesn't. I've had modems both ways -- my current ISP rental modem doesn't while the previous one (which broke so I had to replace it with my current POS modem) did. So in such case, you have to vnc://192.168.x.x of the "vnc server" computer when you are on the same LAN.
You are aware that on the client (school) machine, screen sharing preferences can be set to encrypt all data on the connection, not just the username/password negotiation piece, right? I don't know whether that setting persists across sessions or only persists for the duration of the current session. I wouldn't want my client mouse/keyboard and "server" screen video to be transmitted in the clear; that's why I bring this up.
Does that answer your question? Or did I totally misunderstand what you were asking?