Q: Screen sharing w/ Yosemite not working
Hi all,
I am trying to do Screen sharing from Yosemite MBP to Yosemite MBP and it will not let us. We are both logged in and texting etc. but even when we ask the person to share their screen and they say allow - nothing happens....
It used to work...
Teamviewer works fine...
Q: Any way to get this working?
Is it a bug?
MacBook Pro, OS X Yosemite (10.10.4)
Posted on Aug 7, 2015 2:35 PM
Hi,
Messages and iChat before it uses a process called SIP (Session Initiation Protocol) to connect two or more people for A/V and Screen Sharing when using AIM, Jabber or Bonjour accounts.
VoIP systems also uses this as does Skype.
Somewhere along the line a server has to connect the two.
This is very much like an old fashioned Telephone exchange with people.
It is a text based protocol so it includes instructions and steps such as Ringing, Trying, Inviting and so on.
More https://en.wikipedia.org/wiki/Session_Initiation_Protocol
Technically there are internationally agreed ports that are supposed to be used.
On the Internet Back bone and to a certain extent ISPs are supposed ( I stressed supposed) to not interfere with SIP traffic.
However back during iChat 3 which Added Jabber Buddies to the iChat set up a lot of ISPs world wide started to close the SIP ports and demand extra money to open them up again.
The regular posters at that time used to suggested that people contacted their ISP for Breach of Contract which solved things for some people.
At iChat 4 Apple moved the SIP function (Skype never seemed to use the ports from the beginning).
The server that does all this stuff for Apple is their SNATMAP server (Originally snapmap.mac.com)
It is only used by Apple for the A/V chats which includes the Audio Chat alongside Screen Shairng connections in the accounts that iChat can do Video chats for (AIM, Jabber and Bonjour).
These continue into Messages but does not included the iMessages variation added in Yosemite.
Once the SNATMAP server has connected the people involved then it drops out of the process.
As you start up iChat or Messages it is also used to test the Bandwidth speed you have (that is not mitigated by either Older OS and Quicktime settings or the Bandwidth Limit in the app).
This form of chatting is AIM to AIM or Jabber to Jabber or Bonjour to Bonjour.
You cannot connect across services (not even to the iMessages one in Yosemite).
However as all IDs nowadays tends to be based on email IDs anyone can be added to a Buddy List. (or in the case of iMessages anything can be an Apple ID).
With the advent of Yosemite's Screen Sharing from within the iMessages account it could mean a lot of unconnectable attempts are being made causing a drain on the server.
The Hosts are now aware (and have posted they have read it and done something with it).
Now it is a waiting game.
It will either turn out to be SNATMAP and Apple will do something about (albeit silently) or it will turn out to be something different in which case Apple wil probably lean on the people concerned and we still will not know anything until it all starts working again.
8:12 p.m. Thursday; August 13, 2015
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
Posted on Aug 13, 2015 12:12 PM








