iOS 3 already supports CalDAV/iCal Server
I use iCal Server on my Linux server (from macosforge) and I have no problem accessing my calendars from my iPhone. Apple even advertises iPhone support on their website http://www.apple.com/server/macosx/features/ical-server.html
What doesn't work is syncing via iTunes. Your calendars won't be recognized as CalDAV calendars. You have to set them up manually.
the phone removes the port number but puts it into the advanced tab, i guess (happens for me, too).
You can also test if the phone actually able to connect server by simply using your browser. Just browse to http://example.com:8008 or https://example.com:8443. A username/password dialog should pop up. If you are able to log in you can at least be sure it is not a networking problem or a wrong username or password.
Cool trick! Didn't think of that. I am able to log in, so at least I know I'm using the right username/password and the server is working. Thanks!
Well, I'm slowly running out of ideas why it won't work on your phone
Does it work with iCal? Maybe you need to create a calendar for your user first.
Here are some instructions on how to setup CalDAV for various clients: http://trac.calendarserver.org/wiki/CalendarClients. Maybe you missed a step in the setup process.
OK, so after I posted that I tried going to my server using Safari (like you suggested), but on my phone. (I just tried from my laptop before). My computer gets to it fine, even from outside our office network, but my phone won't when I'm connected to our wi-fi network.
So I turned off wi-fi on the phone and, lo and behold, I was able to set up the calendar on my phone!
So I guess the next question is, why can't my phone access my network via the outside url from within my network? My computer can. Gotta be a DNS setting somewhere, I suppose, but the DNS settings within my network should be fine.
Edit: And it doesn't look like you can view delegate calendars on the iPhone, right? I'm not seeing any of them, anyway.
It's hard to tell without knowing your network configuration. Could be a NAT/port forwarding or firewall problem. Do you use the same Wifi for your Macbook?
That might be. I never used the more advanced features of CalDAV, but I have heard that there a some limitations on the iPhone.