You may find the following doc useful. Note that environment variable ORACLE_HOSTNAME can be used for specifying a host name.
By the way, have you checked if there is a listener listening for this database?
Ensure you follow all steps to configure your DBcontrol as per below metalink doc
Configure DB Control 10.2, 11g for use in Active/Passive High Availability Environments (Doc ID 362524.1)
Regarding listener error I think the issue is because of the machine has multiple NICS/IP addresses and the hostname used by EMCA does not match the hostname used by the listener or the etc/hosts file is not correct
If the Listener is up on virtual host. Set environment variable ORACLE_HOSTNAME=<virtual host>
Also refer to below metalink doc to help resolve the issue
Troubleshooting EMCA Failures Due to Database Connectivity Issues (Doc ID 1106623.1)
Also check the <ORACLE_HOME>/cfgtoollogs/emca/* for detailed error message