Summary: Zoo requires access to TCP Port 80. This is not possible on systems with Web Services running.
When I restart my server, the Zoo service does not start. When I check the Windows Event Log (Control Panel → Administrative Tools → Event Log), I can see that the Zoo service logged an error:
The Zoo service on the Local Computer started and then stopped. Some services stop automatically if they are not in use by another service or program.
Examining the details of the error, again in the Windows Event Log, the following is reported:
Address already in use by another process. Run 'netstat -o -n -a' from a command line to find the conflicting process ID, then look in Task Manager to find the name of that process.
The reason for this error is that some other application is already using TCP Port 80. Only one application can listen to a port at a given time, so Zoo fails to bind to TCP Port 80. More common applications which cause this include: