CometChat v3.0.9 and higher versions, provides full cross-domain support. You can run CometChat across multiple domains/sub-domains using this feature.
An ideal use of this feature is when you have CometChat installed at www.yoursite.com and also want to use it on abc.yoursite.com.
To use CometChat across multiple sub-domains, follow the steps listed below:
Edit cometchat/config.php and set BASE_URL to the full path e.g. http://www.yoursite.com/cometchat/
Then set CROSS_DOMAIN to 1
Add the following code to the site template of your sub-domains (remember to include the full URL path).
Add the code immediately after tag:
Your users must be logged into your main site inorder to use CometChat in your sub-domains.
Use of CometService or alternatives is strongly recommended when using CometChat in cross-domain environment.