Possibility that Screen Sharing might support multiple simultaneous account sessions?
Generally when screen sharing you are connected to another system and are served whatever is being output to the monitor. In the sharing preferences you can select which accounts can use this feature, but there is nothing you can change about the overall functionality of the feature, which is to display the current contents of the screen to a remote location. Despite this, one user mentioned a small glitch that enabled him to essentially log in to the remote system in a separate account, and not see what was displayed on the remote screen.
Apple Discussion poster "denmoff" writes:
I've just upgraded two of my macs to snow leopard from leopard. I have two accounts, one is mine, the other is my wife's. My wife logged onto the iMac (the remote mac) with fast user switching turned on while my account was also logged on. When i used share screen from my macbook to my remote mac with my account, i got my account screen instead of hers. She continued to use her account with out any interruption from me. I could open apps and do as i please on the imac while my wife did her thing. This is not how it used to be with Leopard. If i used screen share, i would take control of her screen. My question is, is this supposed to happen? its kind of neat that it does this, but what if i want to control her screen? There isn't an option to change this."
This bug reminds me of similar situations I've seen where two separate functions have been melded together due to a glitch. For instance, in the game Quake 3 you could only start an internet server that ran in the background if you were not actually playing the game, or you could start a local network or "single-player" game. Despite these three options, I once played a game of Quake 3 where I started a local game to play with a few friends on the local network, but the game ended up broadcasting to the internet as a server for anyone to join. It was unsupported, but some glitch allowed it to happen.
Glitches such as that in my Quake 3 game and screen sharing expose the possibility for new functionality, which makes me wonder whether or not the programmers intended future support for the feature. For Screen Sharing, it would be exceptionally useful to log in from another system and choose either to view whatever is currently on the screen, or to see only your account privately but still allow others to use their accounts on the system. I imagine this would be exceptionally useful in a variety of scenarios; however, the closest that Apple has come to this so far is to have a "curtain" mode for Apple Remote Desktop. This locks out the local screen from anyone physically sitting in front of the computer so a screen sharing session can be private, but even this only allows for one physical user at a time. Support for multiple separate but simultaneous login sessions would be a boon to screen sharing.
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If the above post means that Snow saves you from having to run VNC Server, that's great. But I can't use it b/c Mac "A" can't run Snow :-(
OS X screen sharing uses the VNC protocol, and I have used this to advantage on both Leopard and Snow Leopard to "share" a user session other than the one on the monitor.
Here's what I do:
- Leave OS X's screen sharing off. (I don't think this is necessary, but it makes it simpler.)
- In my user session, I run a utility called OSXvnc, which initiates a VNC share (which, as I said, is the protocol OS X screen sharing uses). Use the defaults. Do NOT use OSXvnc's "Configure Startup Item", which sets up OSXvnc as a system-level VNC server like Screen Sharing.
- Feel free to switch out of the user session running OSXvnc.
- From another Mac, select "Share Screen..." with the Mac running OSXvnc. You should be connected to the user session running OSXvnc.
Exercises left to the user:
- VNC sessions use "channels" on the TCP port; the default channel is 0. It should be possible to use one channel (such as 0, the default), for the "default" behavior of screen sharing, and other channel(s), such as 1, for per-user sessions. Theoretically, multiple users could log into sessions not necessarily rendered on the display. Note that I say "theoretically."
I think Apple could leverage their implementation of VNC to support this officially, but I don't see them as being motivated to do so. The result would be a (simultaneous-)multiple-user Mac. Or maybe they would support it, if you imaging a pricey, powerful, home "server", on which you could run multiple remote user sessions from lightweight laptops or even (dare I say it?) tablets...
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by Fingal
November 5, 2009 9:40 AM PST
- Screen Sharing vs. Microsoft Remote Desktop Connection (RDC) is one of the few areas where Windows is way ahead of the Mac. RDC performs better than Screen Sharing (or VNC). You can connect and login as any user, even one that wasn't already logged in at the machine. There's no need to specify different ports for different users. Also rather important, you can specify screen resolution from the RDC client. Try Screen Sharing from a laptop to a Mac desktop with dual Cinema Displays. It's just about impossible. Screen Sharing scrunches the full resolution of both displays into one window and reduces it to the point that you can't see a thing.
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by tkessler
November 5, 2009 10:46 AM PST
- Unfortunately I'd have to agree there as well, specifically with how objects are rendered. Microsoft's solution is very quick and feels like you are in front of the computer. There is some lag, RDC seems to have the remote system draw items instead of sending a series of screenshot updates.
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(6 Comments)As for resolution issues, you can change the remote system's resolution or you can turn off scaling in Screen Sharing, which will end the scrunching of the desktop.