Checking http port [80]: already bound ERROR: The http port [80] is already bound. Splunk needs to use this port. Would you like to change ports? [y/n]:

On a Solaris machine, I modified $SLUNK_HOME/etc/system/local/web.conf to use httpport = 80
The below error was then presented when trying to start splunk-web:

 Checking prerequisites...
 Checking http port [80]: already bound
 ERROR: The http port [80] is already bound. Splunk needs to use this port.
 Would you like to change ports? [y/n]: n
 Exiting....

The following did not reveal any other port 80 uses

> netstat -an | grep 80
---
> telnet 127.0.0.1 80
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused
telnet: Unable to connect to remote host

I was also unable to telnet to port 80 from another machine TO this machine. Port 80 was not in use. What else might have caused Splunk to report port 80 was already bound?