Like most things there is an alternative way of doing this.
Basically it is using the method to set up a New Account (Screen Name) when you have not actually set one up in the first place as it is possible to Click through the Start Up Screens.
Go to the iChat Menu and select Preferences.
The next window will show a range of icons across the Toolbar and you want the Accounts one to be Highlighted/selected. This is a bigger pane than in iChat 1 or iChat 2.
Many things from different panes in the previous version(s) have now been gathered in this pane but have tabs to access them.
You can set up more than one Screen Name and use this same spot to change between them. Starting with the List on the left. At the bottom is the Add + button. This will open a choice in iChat 3 to add AIM valid names listed under AIM and .mac and below a divider Jabber IDs
So if you have got here with no Screen Name entered in the Start Up Screens enter the Information now after choosing either AIM, .mac or a Jabber ID type.
Dealing with an AIM valid Name you get to have a pane that is similar to the Welcome Screen version in that you can change the type between .Mac (@mac.com) and an AIM name. Leaving the Password blank will get iChat to prompt you each time you try to Log in to AIM. Otherwise it is stored in the Keychain like other passwords.
The Name is then added to the List. Second, third or more Names can be added in the same way.
You then get to see the Information tab filled out with the info you just entered. You get to select which one is Active if there is more than one and whether iChat logs that Name in when iChat is started up.
If you are logged out then you can change the Description (how the name displays in the List and in the iChat Menu for Switching Accounts there or Logging In and Out or in the Window Menu when Logged in).
The Security Tab
This is the stuff that was the separate Privacy Pane in iChat 1 and 2. It only applies to AIM valid names (AIM and .mac)
It has the same methods of saying who see you as On-Line.
Allow All does what it says. Allowing Buddy List Only means that only those people in your Buddy List can see you as On-line. Specific People can be used at various times so that you could only have Friends and not works contact when at home for instance.You have to add people to the list via the Button alongside. Block All speaks for itself. It is not the same as Invisible in iChat 4 as you can not see who is On-Line either but it does save Logging out or Quitting iChat when you want to get on and do something. Blocking Specific People I find is very useful. As I test with people want them to be able to contact me but once in a while I do find someone who seems to have no Social Skills and not respect Away messages
The Server Settings Tab
The content is available to use when you are Logged out of AIM.
When you click on the Server Settings tab it will show you the Server name and the TCP port that iChat is using to Log in to that server with. The default server is login.oscar.aol.com and the port is 5190. (There are no longer any other servers available) (Please Note the picture is an iChat 4 one that can do an SSL Login which changes the name to slogin.oscar.aol.com but ichat 3 can not use this name,)
The port can be changed (when you are Logged out of AIM). The reason for this is that iChat uses Port 5190 on the TCP protocol for Logging in and sending basic Text Chats and also on the UDP protocol for File Sending and Direct chats and some modems and Routers that have to use Port Forwarding do not like this dual use - so changing the port here is useful. (Port Forwarding only allows a Port to be forwarded once to one IP and some devices insist and list Protocols as well which makes it seem the port is to be forwarded twice)
From testing it seems that the AIM servers will actually accept a login on any port (there are, in fact, 65535 of them). The suggestion is to use one below 1024 as these ports are always open in a routing modem or router. On the whole we recommend using port 443 as this is used by some mail applications and secure Websites and will also be open in the Mac Firewall in versions up to Tiger (10.4.x).
If you use a Proxy server to get on to the Internet this is also where it is set, although generally iChat seems to do better with use of the System wide Proxies set in the System Preferences > Network pane.
The Server name will be where you got your Jabber ID from. Your ID will be in an email type format and when you add the name iChat will take the suffix as the Login Server's Name and fill in the Server Settings for you. Most Jabber Servers also use port 5222 to Login.
There are exceptions to the above most notably Googletalk. If you Login to your Account Google (Mail) you can enable Googletalk and connect to their server via iChat. However as it uses your Googlemail ID as the Google talk ID iChat thinks the server in Googlemail.com and it needs to be changed to talk.google.com The Login port it uses is also different and you need to check it list port 5223 as well. See here for more
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