IChat screen sharing security/encryption

I'm going to be using iChat for the first time and want to use the screen sharing feature between two computers running 10.6. iChat's documentation says:
"While every screen sharing connection uses encryption, the highest level of security requires both participants to have MobileMe subscriptions with encryption enabled. If this is the case, you will see a lock icon in the screen sharing window."
Neither I nor the person I'm going to do screen sharing with has a MobileMe account. I'm wondering:
1. What is the difference between the encryption that "every screen sharing connection uses" and the enhanced security allowed with MobileMe accounts? How does this compare with, say, doing VNC over an SSH connection? Is it adequate for the usual "family help desk" tasks, which may involve typing passwords?
2. I understand that one can get a free MobileMe account which only has iChat capabilities. Does this free MobileMe account enable iChat encryption, or do I have to pay to get that?
Thanks!

re 1)
I am not aware that Screen Sharing is claiming to be Encrypted in each and every connection.
As far as I am aware it uses a modified Apple Remote Desktop engine and is a VNC connection tied together with a Audio Chat (two separate Ports/Data streams in tandem) and that a problem connecting either part will result in failure of the whole connection.
It is claiming to be encrypted in each and every connection -- as I quoted in the original post, "While every screen sharing connection uses encryption..." This is from http://docs.info.apple.com/article.html?path=iChat/5.0/en/17157.html

Similar Messages

Screen sharing security?

I'd be interesting to hear thoughts on the security of the screen sharing feature of Leopard.
Is the content of the interaction protected or encrypted in any way?
How easy would it be for someone to engineer a screen sharing 'attack' on a computer (without the users consent, obviously)?

iChat Screen sharing requires that you Accept the call.
It also contains an Audio component so you can talk to the person involved.
As with any iChat A/V related chat it is Peer-to-Peer on a 1-1 basis.
Given that it does go through many server on the internet between you and your Buddy (like a telephone call would) it does not go through the AIM servers like a plain text chat does.
On the other hand the data is not encrypted unless you both have @mac names and IF anyone was actually at those Internet servers in between the data could be read.
However you can end a Screen Share with the keystrokes Control+Esc
From iChat Help
*About screen sharing security*
When you share your screen with a buddy, the buddy has the same access to your computer that you have. Share your screen only with trusted parties, and be particularly careful if you receive a request to share your screen from someone who isn’t in your buddy list.
If the request comes from someone in your Bonjour list, remember that the person’s name is not necessarily accurate, so his or her identity is uncertain.
While every screen sharing connection uses encryption, the highest level of security requires both participants to have .Mac accounts with encryption enabled. If this is the case, you will see a lock icon in the screen sharing window.
If you need to quickly end a screen sharing session, press Control-Escape.
Realistically it as dangerous as opening an email that you don't know the origins of and then opening a file contained in it.
I personally have not tried transferring stuff from one computer to the other.
So I don't know if there are any alerts to say a file is being sent. I would expect a progress bar at least but then again this may not be the front window.
There is/was one Virus that was in the wild for the Mac OS X.
It did involve iChat.
To get it you had to have been sent an email and open what looked like a .jpg file.
It would then spread to your other Bonjour Contacts via iChat.
i.e. you had to do quite a lot yourself to actually get this virus.
Ryan M who posts in iChat 3 posted a fix.
In terms of how secure compare it to having to login in here at Apple.
It's over the net and you have the control to end it but it is possible for people in the right place at the right time to read the data.
if you give info away about yourself here such as your ID and password then people could use that (but the login page itself is a secure page).
These questions are always hard to answer as an idea of a security risk tends to be a personal thing.
10:26 PM Wednesday; June 4, 2008

Ichat Screen Sharing will not work no matter what I try...

I have read all the forums and can't find an answer. Something that should be so simple such as screen sharing through iChat (as advertised) is virtually impossible. This I can not explain. Especially since video chat works!
Both computers in question here are macbooks, both have leopard, both are or wireless networks. Is the router blocking the connection and if so, why will it allow video chat but not screen sharing?
There is either something real simple that I am missing here, or this is not possible at all.
some things that i have tried:
disabling stealth mode
on the firewall, enabling incoming traffic from ichat
made sure screen sharing is enabled in ichat
made sure the settings were the same on the remote apple computer
tried unchecking everything in the sys pref "sharing"
Both of the parties involved are using the same ISP, this really is mind boggling.
Is this a bug that is being fixed or what? I am not trying to perform a miracle here, but this is getting ridiculous.
If this is a router issue, apple should release some documentation on how to configure ichat screen sharing through your router.
If anyone has had this problem and has a fix, I would love to hear it. Keep in mind I have googled this many times and tried just about every piece of advice that I could find on this.
Thanks

iChat Screen sharing does not as such for the screen bit use the Video/Audio port.
The Documentation was lacking last time I looked.
This one tells you the port changes in Leopard http://docs.info.apple.com/article.html?artnum=306688 compared to Tiger
Tiger is linked in the first to here http://docs.info.apple.com/article.html?artnum=93208 where most of the other ports are.
However Screen sharing was not part of iChat 3.
If you do a Quick Look at the .plist(s) you will see the reference to ARD which is Apple Remote Desktop which is what the screen ending part is based on.
This Doc will tell you which ports ARD is likely to use
http://docs.info.apple.com/article.html?artnum=106439
(It says 5900 and 5988)
This should be allowed through the use of UPnP in your routing device or specifically opened.
Now the not so good news.
I run Little Snitch, A utility that tells you ports and IPs of incoming and outgoing network connections by any app you have.
This has told me that in fact the Screen port seems almost completely random normally in the 50000 range of ports
It may not be all you wnat to hear but I hope it helps.
9:57 PM Tuesday; February 12, 2008

IChat screen sharing does not work on my Mac Pro

I have a weird iChat screen sharing problem that i can't seem to resolve on my Mac Pro. Ever since i got my Mac Pro in early 2008, using the screen sharing feature in iChat has always been flaky. I have never gotten to the point of getting it consistently working. Lately, i have not been able to get it to work at all.
Most of the time, when i choose to share my chat target's screen (or when i share my screen), i would be able to see my chat target's screen and use the mouse for several seconds before the shared screen session is ended. The errors that i am getting are:
+"Disconnected from Screen Sharing because:+
+No data has been received for the last 10 s..."+
+"There was a communication error during your chat.+
+No data has been received for the last 10 seconds. You can send+
+details about this problem to Apple to help improve future versions of+
iChat."
On other occasions (mostly when i am trying to troubleshoot this issue by testing in the same network with my Powerbook, which is on 10.5.6 as well), i get this error:
+"Disconnected from Screen Sharing because:+
+Screen sharing could not be established."+
I have tried to do screen sharing via iChat with other Macs in the same network and also on the internet but with the same problems.
Initially, i thought this may be router related. But the fact that iChat screen sharing on my Powerbook works perfectly both in intranet and internet eliminates my router as the culprit.
I have also tried disabling the OSX Firewall but the outcome was the same.
I read some posts that there may be issue with using the external iSight web cam. I unplugged it, cleaning up all the iChat-related caches and preferences and tried again but with the same result.
I have also tried connecting to iChat using several different account types (mobileme, .mac and AIM) but the end result is the same.
I run a Ubuntu VMWare fusion VM on my Mac Pro as my webserver. I thought that may be the problem. Shutting down the Ubuntu VM also does not help.
Applecare support personnel also instructed me to re-install iChat but that did not help as well.
One interesting error i noticed in the system.log (seen via the Console app) that is generated everytime iChat screen sharing fails on my Mac Pro:
+12/23/08 12:32:00 AM /Applications/iChat.app/Contents/MacOS/iChat[507] error getting server version+
I am really running out of ideas on what else i can do to get this resolved.
Thanks in advance for any suggestion.
Message was edited by: Changren Yong
The audio and video chat portions of iChat work fine.

I managed to make some headway in my attempts to troubleshoot this problem. I did a fresh Leopard install on one of the drives in my Mac Pro. I then proceeded to update it to 10.5.6. After that, i launched iChat and attempted screen sharing with my Powerbook. The first few attempts failed, with the following symptoms:
- i would be able to see and control the Powerbook's screen
- after 5 seconds, my screen sharing session is disconnected
I then unplugged my external iSight. After i relaunched iChat, i managed do screen sharing in iChat without being disconnected!!! When i connected the iSight back into the ACD, with iSight off, i attempted to screen share again. This time, it failed after about 5 seconds, just like earlier. I then turned iSight on. This time round, the screen sharing session was not disconnected!!
So in addition to the iSight issue, something in my original Leopard startup disk is causing iChat screen sharing to fail because even when screen sharing was failing on my fresh Leopard install, i do not see this error:
/Applications/iChat.app/Contents/MacOS/iChat(507) error getting server version
So if i can figure out what is causing this error to show up in system.log, then i can manage the iSight issue.

IChat Screen Sharing will not work when VNC will?

I am finding it impossible to get Screen Sharing working via iChat. I'm not surprised, as iChat seems extraordinarily balky at doing anything other than text chat. However, what confuses me most about this is that the Connection Doctor 'Capabilities' tab suggests that the net connection for my family members (1024/128) is "too slow" for Screen Sharing - yet I have been using OSX VNC for two years perfectly successfully to do so?
Does using Screen Sharing directly have the same limitations?

Hi,
In System Preferences > Quicktime > Streaming change the Speed to 1.5Mbps
This should change what iChat sees as being Capable off once you restart iChat.
The VNC app Screen Sharing that Opens form the Finder > Go > Go to Server VNC:// does not include a Audio component.
This uses less bandwidth than the iChat Screen Sharing which does include an Audio stream.
Also the Screen Sharing is done on a separate port to the Audio part and from testing seems to be a random choice.
For this reason we have been suggesting using UPnP in any modem or router to allow ports.
Apple have not said what ports it uses
http://support.apple.com/kb/HT1507?viewlocale=en_US Tiger A/V ports and Bonjour and Jabber
http://support.apple.com/kb/HT2282?viewlocale=en_US Leopard A/V ports (It should say but does not that you still need the Jabber and Bonjour ones if using them).
This doc http://support.apple.com/kb/HT2020?viewlocale=en_US says you need iChat to see at least a connection speed of 128K UP and Down for Screen Sharing.
It is known that iChat Screen Sharing is based on Apple Remote Desktop but it does not use the same ports (5900 and 5988).
2:06 PM Saturday; January 10, 2009

Does Ichat screen sharing work properly with Lion OSX?

Hello, I am planning to install the new OS Lion soon. However, I was wondering if the Ichat screen sharing works properly with Lion. I use the screen sharing quite a lot to communicate with my co-workers, so it's a deal breaker if the app crashes when using the screen sharing option. Thank you!

Hi,
I have not seen a post where it has been reported to be a problem.
9:12 PM Friday; August 12, 2011
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb( 10.6.8)
 Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images."  No, Seriously

IChat Screen Sharing: Audio works but video is a white screen.

I am having a problem using iChat screen sharing with a specific computer. We are both running OS 10.7.4. I have a Mac Book Pro (fall 2011) and he has a iMac one to two years old. We have tried contacting apple support but no luck yet. We tried setting up a test user to see if the problem was user specific but encountered the same problem. Again, video and text chat work fine. He can share my screen with no issues. Only when I ask to share his screen do I get a blank white screen. Audio works and I can manipulate his curser but all I have is a white screen. I have tried changing the resolution on his iMac but this has not helped. Also we are both using Google Talk as the chat server.

Hi,
Historically iChat Updates came in OS updates.
Not every OS update had an iChat update but that was the way they were delivered.
Only twice during the lifetime of iChat 3 have there ever been standalone Updates outside of this.
Most Updates are now through the App Store but Software Update can still be used (I have mine set on Daily despite Apple's Updates normally coming on Tuesdays)
One person stated he thought there had been a change with OS 10.8.1 saying the Build number of Messages had changed.
In my experience it has not and when Apple do update something the build Number and Version number change.
It is widely know that Apple send Developers and others advance copies of the OS to try out.
Those people sign NDAs (Non Disclosure Agreements) so you will not see any discussion of any up and coming stuff on this site.
8:55 PM Thursday; September 6, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
 iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images."  No, Seriously

A refinement for iChat screen sharing

Leopard's iChat screen sharing is a great feature, and I'm teaching various of my relatives how to use it so I can help them more readily. However, there is one refinement that could be added to it that would increase its already great utility: the ability to rapidly switch from sharing one screen to sharing the other, in a two-participant session. To do this now, as far as I know, the session must be terminated and restarted, and this is inconvenient.
One way I can imagine this working is to have a third option: share both screens; the initiator is thereafter allowed to switch back and forth between the two screens, making the chosen one visible to both parties.
And while I'm posting, I'd like to say that the continuing interference by Comcast in iChat Video Chatting that I and many others have reported on over the past year or two seems not to arise in screen sharing. Let us count our blessings in that regard, and hope for a resolution of the overall problem.
Tom DeBoni
Oakland, CA

Hi,
Change the resolution on the Older OS.
It is the only workaround we have found at the moment.
9:05 PM Wednesday; October 17, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously

Fix for iChat Screen Sharing Problem I was Having

Okay, I just thought I'd chime in and try to help some people from going through the frustration that I recently went through with iChat in Leopard. Here's my story.
iChat screen sharing used to work for me and suddenly one day it stopped working correctly... lemme explain. I would let someone share my screen, and it would start working and they would wave their mouse around and 10 seconds later, it will freeze and lose connection with a timeout.
At first I thought it was a firewall issue but, after thinking about it.... I thought, how could it be if it was working for 10 seconds and suddenly stopped? If it was a firewall issue, it wouldn't work at all. Then I thought maybe my iChat app got corrupted, so I used Time Machine (yay!) to restore iChat from one of the first days I got Leopard. That didn't work. So then I figured my preferences got corrupt, so I deleted my com.apple.ichat.plist file and still didn't work. I was so mad that Apple made this feature basically useless for me until I had a crazy hunch.
After an hour if pulling out my hair, I finally had an idea of what might be causing the crash... I noticed I had my old iSight plugged in (the external firewire iSight) into my Apple Cinema Display. I unplugged it and iChat screen sharing worked PERFECTLY. You should also know that I don't have problems with my iSight, it works well on Video Chat and Audio Chat and even presentation mode but, it screwed up screen sharing.
In conclusion, if you're experiencing sudden connection losses with iChat screen sharing, check to see if you have an iSight plugged into your Mac and unplug it.
Also, you're welcome.

Thomson-Alcatel 780 modem.
Unfortunately this is going to needs a new modem (or Bridge this one and have a router)
Read this section http://www.ralphjohns.co.uk/page4a.html#_text
Although the SIP Binding to port 5060 in this device could be UnBound in Version 4 firmware it has not been fully Unbound in Version 5 or 6 (Despite the version 5/6 instructions further down that section).
The problem can make the iChat issue look intermittent with it working with some Buddies and not others.
Getting a new modem that does not have SIP binding is the only realistic way around the issue (Or setting the device to Bridge and having another router)
11:00 PM Friday; April 25, 2008

IChat Screen Sharing Stops when Switching Between Displays

Hi. Have been doing iChat quite nicely with my Dad for years and now I have a problem. Running current Snow Leopard 10.6.2 on both Macs, iChat 5.0.1. I usually hop onto his screen to help him solve problems, answer questions, do updates, etc. Until very recently, I have been able to switch between his desktop and mine by clicking on the small alternate display window. I could work on his computer and mine by simply switching between them in this manner. Now, suddenly, iChat screen sharing stops when I click on my display in the small window. This action returns me to my display, but the screen sharing session ends and I need to request it again. Any idea what might be going on here? I'm stumped. Thanks.

Hi,
Is there any chance you are clicking on the top left hand corner (where the red blob would be) as this will Quit Screen Sharing ?
10:13 PM Friday; January 15, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"

IChat Screen Sharing mouse problems

I just bought a new iMac 20" for my mom for xmas with the thought that the iChat screen sharing will help me to remotely configure her system.
I am finding that once I have initiated the screen share I am have erratic mouse behavior. When I am sharing her screen and moving the mouse the cursor will jump around the screen. this happens even worse if I am click-dragging a window around.
Is there any way to improve this performance? At work I use Windows remote desktop with no issues such as this, and I would expect the same performance from OSX.
Thanks

My first thought is that your mother is also trying to control the mouse.
I presume though you have exclude this.
iChat Screen Sharing does include an Audio component so the computer is doing an Audio chat at the same time effectively. This will have a impact on the processor usage particularly over the way iChat A/V chats use the processor. (they tend to dip in and out to spread the load and not hog the processor).
10:11 PM Friday; January 9, 2009

IChat Screen Sharing - I can share my screen, but Dad can't share his

Hi all,
Last week I used iChat screen sharing to help my Dad with his iMac, and although it froze and dropped out frequently, it was working.
This week, for some reason we can only share my screen, but not his. On both sides, the option to share his screen is disabled (greyed out). Also the Video > Screen Sharing Enabled menu item is also disabled on his Mac, but mine is enabled and turned on.
Both of us have Screen Sharing turned on in System Preferences > Sharing, and both have set to allow access to anyone.
He restarted his Mac a couple of times, but no luck.
Has anyone had the same problem, and is there a solution? Any idea why it would work last week but not this week?
Thanks in advance for any help you can offer.
Will.

Hi,
You can come back and change the marking of the answered or not so that is not a problem.
What it should help is stop other people joining in (an effectively loading you with email alerts when they do).
A good specific title like your should also help.
9:00 PM Tuesday; November 27, 2007

IChat screen sharing and video not working on MacBook but works on Mac pro

I have a MacBook and MacBook pro. Both have the lion os 10.7.2. I can use iChat on the MacBook pro for screen sharing, video chat, and text chatting, with others remote to me. However, I can only do texting with the MacBook. I can do screen sharing via Finder between my MacBook and MacBook pro. I can do FaceTime between both systems. I can also do FaceTime between the MacBook and anyone remotely.
I also tried installing teamviewer on the MacBook, and on a remote MacBook..... And I get the same results where I cannot share the screen, from the one that has not been working.
I have checked the settings under system preference and made sure screen sharing was enabled. I have checked under iChat under video to make sure screen sharing was checked.
The macbook that is having this problem is configured for AIM for iChat
I have run out of ideas. Any suggestions on what I might try?
Thanks

Ok,
I will list the ports in greater detail and point out when iChat uses them.
AIM Login and 1-1 Text Chatting
iChat version 1 through 5 will Log in to the AIM server on port 5190 (TCP Protocol) by default.
Since iChat 2 we have been posting here that the AIM servers allow a Login on almost any port and have been suggesting port 443.
This is used by both Web Browsers for secure Login to some sites and by the Mail app with some mail servers.
It is also below port 1024 (most domestic routers have the ports above this figure closed) In some campus situations using port 443 will normally allow at least Login and Text chatting.
iChat 6 uses port 443 by default.
File Transfers (AIM)
When doing File Transfers with AIM Buddies iChat will move to using Port 5190 on the UDP Protocol.
This cannot be changed. (This invokes the little Message about Starting Direct IM in an open Chat)
It also uses this port for Pics-in-chats, dropping Files on a Buddy's name with out a Chat or sending other files that are not pics.
In the case of Port Forwarding some devices don't like port 5190 being forwarded "twice" which is another reason for moving the login and Text chat port.
Jabber Logins
No matter what Jabber server you use ichat will use one of two ports (5222 and 5223)
Which one it uses is dependent on whether it needs and is using an SSL Login or not.
SSL Logins use port 5223 and NON SSL one use 5222 (ticking or Unticking the SSL box on a Jabber account will automatically change the port).
Google Talk is the exception in that it allow a Login on port 443 as well.
The First Apple Doc I linked you to says iChat uses port 5220 in Jabber.
I run Little Snitch and have never seen any version of iChat use this port at any time.
Bonjour
Any Mac to Mac Connection or Mac to any Bonjour able peripheral will be on port 5353.
This is normally opened (Preset) in the Mac Firewall for the Finder/System side of Sharing.
iChat needs and uses two other ports (5297 UDP and 5298 on both TCP and UDP)
As they an LAN Side connections the router would normally pass them.
At iChat 3 there were issues with the Mac Firewall (it included UDP set up and the preset in the firewall only listed them and TCP so we had people add all the iChat ports (you had to manually enter them in Tiger)
A/V Chats
No matter which Buddy List you start from iChat will do A/V chats the same way.
The Visible Invite you or your Buddy sends is on port 5678 (UDP)
In iChat 3 and earlier iChat then moves to port 5060 to send the SIP Connection Process invite behind the scenes (SIP = Session Initiation Protocol)
Port 5060 is one of 4 ports internationally agreed for SIP (How VoIP phones connect) (5060-5063).
Although ISPs were not supposed to block Through traffic many started blocking End users and then Charging them to open these ports (Many ISP were telecom companies that were losing long distant Telephone calls monies).
The SIP process then in iChat 3 contacts a server run by Apple for this purpose (Snatmap.mac.com to give it it's full name).
This acts like a old fashioned telephone operator connecting the call.
SIP is a text based process.
Your end "Calls" the operator.
The Operator "Calls" Buddy.
Buddy Accepts
iChat then negotiates the ports to be used.
In iChat 2 and 3 it uses 4 ports (vid in Vid out, Audio In and Audio Out) from "the group of 20" starting at the bottom (16384 to 16387 normally)
Three and 4 way chats uses more ports (which is why 20 are set aside)
In iChat 4 Apple realised the issue with the 5060 port and changed the way iChat worked
Since then it has Sent the invite on Port 5678 but then moved to port 16402 (it starts at the top of a smaller group of 20)
All Video and Audio traffic is also now on one port (so no need for 20 ports and iChat now lists 10).
NOTES so Far.
File Sharing during a Chat converts the Chat to Direct IM for AIM Logins
This is Peer-to-Peer in AIM
A/V Chats are Peer-To-Peer and you can actually log out of the Buddy list and continue the chat. (The exception is using iChat 6's AIM Video relay option)
Screen Sharing
Screen Sharing is an Audio Chat with a VNC connection along side.
Both bits have to wok to avoid the Pop-up to send to Apple and the Log that contains.
The Audio part is on port 16402 and the VNC part is random. (So random it is different every time you do it)
The reason it is classed as an Audio Chat+ is so the AppleScript for Auto Accept can filter out Screen Sharing connection and Not Auto Accept them.
This does have a knock on effect as far as your Router is concerned as already mentioned earlier.
You cannot Forward or Trigger the random Port so you have to use UPnP in your router to open the ports.
NOTES
Jabber File sharing may possibly be on port 1080 as listed in the Server Article I linked you to (I have also seen it written about in other stuff I have come across)
However Little Snitch does not seem to confirm this either.
Most time it will be peer-to-peer like the AIM connections for this.
However some Jabber servers do not seem to allow this and have this Jabber65 Proxy set up which passes things Server to Server in between it leaving your end and arriving at a Buddy.
This on Port 7777 but you do not need to open this port (unless you are running a Jabber server)
I have yet to test File Transfers using a Yahoo Buddy List in iChat 6.
AppleCare and Geniuses.
Previously I have been contacted by Geniuses in Stores asking to test customer's iChat.
They and the Applecare people have details about Apple wants an designed the App to work.
What they don't have is the knowledge about what it takes to set it up in the "real world".
There are literally thousands of Makes and Models of routers.
Some like the Thomson-Alcatel brand state they are SIP/VoIP ready but this means the router strips out all SIP Data trying to send it to a Phone.
Early models of Alcatels can get around this with a tweak. Later models can't.
Motorola devices tend not to have UPnP.
Apple Base Stations have Port Mapping Protocol instead of UPnP and this needs setting up.
The Zyxel range definitely does not like the dual use of port 5190 and does much better using UPnP (You almost certainly have to do your AIM login on port 443 with these).
1. I have two computers (MacPro and MacBook Pro) that are both running Lion 10.7.2 and both running iChat 6.0.1. <<-- Fine
2. The Netgear router model is: WNDR3700.    <<<<--- With any Brand there are exceptions and I do wonder about this one
3. The firewall for both Macs is turned on and in the advanced area iChat is listed as being "allowed." <<<<---- Fine
4. In iChat, under the video options, "Screen Sharing Allowed" is checked.                                        <<<<<---- Fine
5. In System Preferences, "Screen Sharing" is checked and this is for "All Users" at present.               <<<<<---- Not Required
6. There are two separate AIM accounts being used for iChat purposes.                                            <<<<<---- OK
7. In iChat preferences, each AIM account is "Enabled" under "Account Information" and the "Server Settings" show the Server as "api.oscar.aol.com" and the Port is "443" and "Use SSL" is checked.                                <<<<---- As it should be
From this and the other info in the first port it was only the router set up that seem to throw some light on a possible cause (Port Forwarding and UPnP conflict)
If just doing Port Forwarding the ports listed would have covered things (Except the Screen Sharing's random port)
Regarding your latest post.
I have table similar to that on my Sagem 2504Fast Modem/router combined device and it too seems to list a different port on the external side on occasions.
I would try the router with the Disable SIP ALG unticked (so it is not disabled). If the Help info on the right gives any info about what this Netgear version does it would be helpful.
Some are like the Thomson-Alcatels I was talking about in that it points the SIP data to a specific place (Possibly a Phone socket on the device)
Others seem to provide an "boost" to enable SIP to work and don't seem to get in the way of iChat.
Try adding the Names in Table 1 from this page and see if you can Video to those.
There are 6 names in total (I am actually only seeing one on Line as I type)
9:19 PM      Wednesday; January 25, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
 iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images."  No, Seriously

IChat Screen Sharing problem on Leopard

Hello everybody!
I've searched this forum but I couldn't find a proper solution to this, at least one that works for me... here goes!!
I've been using my mac for a while now, but for the first time today tried using iChat and Screen sharing with it. I'm having troubles with it, however, even though my chat and video/audio talk is working fine. I know that the problem is with me because my two other friends were able to connect together with screen sharing, but I was unable to connect to either of them. It seems to connect for a split second then it gives the error "Screen sharing could not be established".
1. Screen sharing worked between me and one of the above friends while we were both at my house connected to the same wireless connection. It doesn't work anymore now that we're both at our separate homes. I do know, however, that this friend has the same router as me, but they seem to connect fine with other people.
2. My router is a NETGEAR DG834G. I tried updating the firmware but it says it's either the wrong file or version so I gave up after two goes.
3. I have port forwarded the following ports: 5060,5190,5220,5222,5297,5298,5353,5678,16384-16403. Also by default NAT and UPnP is enabled.
4. I have also tried playing around with the security > firewall settings, with only access to specific applications, and then added iChat. Though I believe I played around with this while iChat was already running.
5. I tried a Remote Reboot of my router (not by holding down the reset button, but through safari)
I know that there are some discussions where people have commented on the same error as me, but I never have seemed to found a solution that has worked out for me. If there are any suggestions that would be fantastic! thanks
-Paul.
Message was edited by: ilovemyjc

Thomson-Alcatel 780 modem.
Unfortunately this is going to needs a new modem (or Bridge this one and have a router)
Read this section http://www.ralphjohns.co.uk/page4a.html#_text
Although the SIP Binding to port 5060 in this device could be UnBound in Version 4 firmware it has not been fully Unbound in Version 5 or 6 (Despite the version 5/6 instructions further down that section).
The problem can make the iChat issue look intermittent with it working with some Buddies and not others.
Getting a new modem that does not have SIP binding is the only realistic way around the issue (Or setting the device to Bridge and having another router)
11:00 PM Friday; April 25, 2008

IChat Screen Sharing Keeps Disconnecting

I recently bought my first Mac and not so good with all the tech talk but I'll try my best. So I was trying to do Screen Share via iChat with a friend who has a 24" iMac with Mac OS X Leopard. I have a 13" MacBook Pro with Mac OS X Snow Leopard Version 10.6.4. Anyways we have tried to connect both ways, screen sharing her's and mine and it doesn't work. It'll disconnect after about 2 seconds, I can hear the audio sometimes and it'll say "Screen Sharing with ____" and then disconnect. I have screen sharing enabled. I don't know if it has anything to do with my router but I'm with Verizon and they provide my wi-fi. I just checked the error log and it says no errors. Thanks to all who try to help me out.
Message was edited by: HuggyLowDown

Hi,
Welcome to the  Discussions
Since the original Post some info came to light that certain ISPs do not seem to allow VNC conncetions. (his/her ISP Verzion is one of these)
iChat Screen Share is made up of two parts.
An Screen Share over the VNC Protocol and an Audio Chat alongside.
As Audio Only chats and Video Chats use the same ports then if you cannot Video or Audio Only chat then Screen Sharing also will not work.
If the Audio part fails then most likely you will get the Pop Up.
I have also seen the Pop up show up if one end has not set the Screen Share Enabled item in the Video Menu (Selecting this toggles the tick On and Off and it has to be ticked).
If a person has Not turned On Screen Sharing then can in fact start the Screen Share as long as they are only sharing Their Screen. (They can not ask to see the Buddy's Screen - nor can the Buddy Start the Screen Sharing).
DOS or SPI will be in the router.
Some devices have it as separate items.
For Instance on a Netgear device it is in the WAN set up page in the menu down the left.
Same for Sagems
Some include it in the firewall.
In this case an Example would be a Netopia which has a 4 level firewall in which High and Medium has both SPI and DOS.
Also a Linksys (on those that have a firewall option in the Security page) have SPI and DOS in the firewall but little info on the screen or in help to tell you
8:58 PM Thursday; October 21, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"

IChat screen sharing security/encryption

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