iChat: screen sharing could not be established

[Joey Cupcakes]

I'm trying to set up screen sharing on two Macs (both running 10.5.3) via iChat's Screen Sharing. The "buddies" are connected and the screen sharing button is available, but whenever we attempt a connection we both see "Failed to start screen sharing because: screen sharing could not be established."

I have used Timbuktu and ARD regularly on both these machines, and made sure the usual VNC ports are open. The machine I'm trying to connect to has UpnP enabled on it's router.

If I try to access using System/Library/Core Services/ Screen Sharing, it connects immediately.

So what preference am I missing in iChat that is producing the error?

I need to clear this up so I can easily help other remote users.

[modelamac]

In iChat, while connected to the other iMac, open Connection Dr. At the top, you will see a "show" button, with Statistics as default. Click on Statistics and select capabilities. Have the other iMac do the same.

There will be 2 Screen Sharing functions listed. Both must have a green check mark by them for both ends of the video chat. Any item with something other than a green check mark won't work.

If all items have a green check mark, you should be good to go.

The other item that could be a problem is any router on either end. Try setting Port Forwarding for Port 5900, forwarded to the internal IP of each Mac (192.168.x.xxx)

This setting will also work for Screen Sharing without the use of iChat. The Screen Sharing app can be found by going to Hard Drive-->System-->Library-->Core Services-->Screen Sharing. Drag this to your Dock.

You can now screen share with any Mac (Leopard) if you know the IP of it. You can share screens if you have Sharing properly set up, with or without involving iChat.

PM me and I can help you test your settings.

[Joey Cupcakes]

Thanks for the detailed response, modelA-

1. I have already port forwarded, as I use Timbuktu and/or ARD regularly (as mentioned above).

2. Also mentioned above, the Screen Sharing app works fine.

I double checked the Connection Doctor as you suggested, and we're all green on both ends.

Regarding port forwarding and knowing the other Mac's IP, if I have to have my 3000-mile away 80 year old dad, for example, go into his router and do port forwarding, the game is over. I was under the impression that if you could chat over iChat in Leopard, you could screen share by pressing a button (assuming sufficient bandwidth on both ends).

[modelamac]

You would only need to get into the router if all else fails.

I believe that if routers are involved, UPnP has to be active/enabled, and my personal experience was that port 5900 needed to be forwarded for screen sharing outside of iChat activity. I can't remember whether it was needed for iChat ss.

Is there a Mac User Group in your Dad's area that might be able to help.

Another thing I just thought of: is the router an absolute necessity? If your Dad can manage this: unplug the power (wall) cord to his modem, take the router out, and connect the modem ethernet cord directly to the Mac, power up the modem, then after a minute or two, the Mac.

I'm sure iChat screen sharing will work with this configuration, and will point to the router as the obstacle in the previous set up.

I don't know that Apple tells you that routers may need fiddling with if involved with iChat screen sharing.

Have you gone to the Apple Discussions/iChat 3 to see if there are any solutions suggested?

[Joey Cupcakes]

[quote modelamac]You would only need to get into the router if all else fails.


Is there a Mac User Group in your Dad's area that might be able to help. I'm really just using my dad as an example. I would like to be able to use iChat screen sharing to help a number of people. It's the supposed simplicity of it that's the attraction over solutions like ARD and Timbuktu. If I can't get it going between my own two machines cross a few blocks- and I (again, supposedly) know what I'm doing- I can't suggest it as a tool for remote desktop help.

I don't know that Apple tells you that routers may need fiddling with if involved with iChat screen sharing.

Have you gone to the Apple Discussions/iChat 3 to see if there are any solutions suggested?

I'll check there. I've looked at all the iChat help files, specific router configuration is never mentioned.