Hi,
This looks very similar to an email I received.
My Answer there was
HI,
As you are aware iChat could video chat AIM to AIM or Jabber to Jabber but not Jabber to AIM or vice versa.
AIM Names can include certain Apple ID and Jabber IDs can include GoogleTalk and Facebook IDs
There are/were several ways to start Video Chats:-
1) Double click the green Video icon in a Buddy list
2) Highlight a Buddy then use the Buddies Menu
3) Right click a Buddy and then use the Video chat option in the contextual (pop up) menu.
Realistically there is no difference in the Messages app. It is still only AIM based and Jabber based Logins
Buddy lists can be revealed from the Window Menu and if you have more than one Account (other than iMessages) the Buddy lists can be separated in the General Pane of the Preferences.
When you start up the app the accounts you have active login to the various servers involved.
Most now use port 443 (AIM and Yahoo) to do this. You can make a Google Account do the same otherwise it uses port 5223 (An SSL login)
This can be important based on your router settings but we will return to that in a moment.
In System Preferences > Security & Privacy > Firewall tab is the Firewall On ?
If it is On use the Firewall Options button.
In here is the Allow Signed Software ticked ?
Is Messages and IMAgent in the Allowed list (the System should add IMAgent once you add Messages and restart).
Presuming that is either set as described or the Firewall is not On then the issue is likely to be the router.
Routers
By default their out-of-the-box set up is likely to be acting as a DHCP server.
The default method for getting an IP on the Mac is to be "Using DHCP" as seen in System Preferences > Network > Advanced Button > TCP/IP tab
This means the computer will hold on to the same IP if it meets the following conditions:-
1) It is on at some point during the lease time for that router (many are 24 hours).
2) that if it is Off for longer then the lease time that it is the only device on the network that needs an IP number when it starts up.
3) you are not swapping between Airport/Wifi and Ethernet connections as these get different IP addresses.
The reason I mention this is it can effect the way the ports needed for A/V chats are opened and whether the computer remains at the same IP.
Port Forwarding is a method of Opening the ports in the router.
Generally you have to list the port (or sometimes a continuous group of ports) and "point" them to one IP (Computer)
Only that computer at that IP can use those Ports which means if the IP address changes the settings will not work.
The reason you have to list the ports is that in total their are 65355 ports (consider them like TV channels)
The first 1024 are open by default and allow Web Browsing, Mail and some other apps to access the net.
iChat/Messages Sends the Visible Invite the Buddy sees on port 5678 (above the 1024 threshold)
Your end needs to allow the response to come back on that port.
After it has the return "Accept" it will move to port 16402 as first choice and send the SIP (Session Initiation Protocol) invite which is a text based connection protocol.
This Confirms the Response was from the same IP the Visible Invite went to and "negotiates" the ports for Video chat (again port 16402 as default)
If port 16402 is not available the app will try the next 9 ports down to 16393 one at a time before trying Random ports.
Example Pic showing iChat 3 ports (there is a typo in the IP box of the "iChat2" line)
NOTE.
Some Routers are effectively SIP aware and try and Filter off SIP data to either IP phones or Connection devices that are used to use regular phones over the internet
These VoIP phones also use the SIP Protocol to connect.
In some cases you an turn this "Off". However in Thomson-Alcatel routers running Firmware after version 4 cannot do this (you will have to change router/Modem)
There are also Add-on Hardware from companies like Vonage that are adapters for Phone that they "suggest" are placed between Computer and router which again will "syphon" off SIP data.
Place them on a separate Ethernet port on the router.
The most useful method of Opening the Ports is to use UPnP (Universal Plug and Play)
This allows the App to say what ports need opening when and closed them after a certain period of Non use.
It also means multiple computers can use the same ports (which in turn means if the Computer's IP changes it does not matter).
AS you say the Buddy is responding with either a Rejection or Acceptance then that would seem to suggest they are using a Mac with either Messages or iChat.
(It will not work to a person logged in via a web browser to Google or Facebook).
The Yahoo Account will not Video (Nor will the iMessages - It invokes FaceTime)
Hopefully somewhere in this will be the piece of info you are needing.
I have a method.
I answer all email notifications of new posts in threads I am already involved with.
I then read all Unread posts tagged with "Messages" starting with the ones that appear oldest (lower down the list)
I then move to the iChat Community and read the Unread ones there.
Basically I will get to reading and in most cases Answering, or adding what I think is either additional info or a different view to replies that may have already been made.
I will get to you.
I understand that some people may want to include more personal info or have not yet made their first post and feel the email route is easier.
Not linking an email to a post that has been made feels like bad manners to me.
Sending an email as well feels like I am getting the hurry up when I discover both routes have been used. (In this case I did answer the email before I got to reading Unread Posts).
Ergo: I am human and likely to interpret your actions that fit my way of looking at the world no matter what your actual actions were supposed to achieve.
Please don't take this in any way than the suggestion of possible consideration of how your actions may be seen.
I may feel completely different about it tomorrow.
It is late where I am and it will be a while (possibly 20 hours) before I get to pick up on any replies.
10:13 PM Saturday; June 29, 2013
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.4)
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