Yes, you can. Do NOT try to run them in the same container application though. (Have one Tomcat for running JIRA and another for Confluence and so-on).
There's nothing special you need to do other than make sure they're all running on different ports and you'll probably want to make sure you've got a decently powerful piece of hardware to run them on.
As Nic said, yes you can. That said, to keep it simple for the users, I've got all of them on separate servers so that I don't have to have any port specification or context in the URLs. Whenever I stand up a new server, I spend the time to weed OUT ports and context in URLs so users can have easy to remember destinations to get to the services. What I end up with, then, is URLs that only need to be typed on any browser as (for example) confluence.corpdomain.com or jira.corpdomain.com and let the app server figure out how to get it there for them.
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