Inaccessible Jenkins

I installed Jenkins on my Ubuntu 12.04 desktop using this guide:

https://wiki.jenkins-ci.org/display/JENKINS/Installing+Jenkins+on+Ubuntu

I also needed to follow this guide:

http://aslamnajeebdeen.com/blog/how-to-fix-apache-could-not-reliably-determine-the-servers-fully-qualified-domain-name-using-127011-for-servername-error-on- ubuntu

From my other machine (mac laptop) I am now trying to access Jenkins via safari:

http://192.168.1.100/jenkins

where 192.168.1.100is the ip address of my desktop computer, but I get a 404 error message. I also tried:

http://jenkins

but nothing happens. What am I missing?

The Jenkins service runs on my desktop PC:

service jenkins status
...
Jenkins Continuous Integration Server is running with the pid 3713

And if I type: localhost:8080in a browser on my desktop, I get the jenkins web interface.

: :

http://www.zzorn.net/2009/11/setting-up-hudson-on-port-80-on-debian.html

.