By default , when we setup enterprise Manager database console(dbconsole), 1158 port will be configured.

But we can change this port easily using emca utility.

In the below example, we will change the port from 1158 to 7100
1. Check the current dbconsole details:

./emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.4.0
Copyright (c) 1996, 2013 Oracle Corporation.  All rights reserved.
https://prdeaidb2:1158/em/console/aboutApplication
Oracle Enterprise Manager 11g is running.
------------------------------------------------------------------
Logs are generated in directory /oracle/app/oracle/product/11.2.0/dbhome_1/prd/sysman/log

Currently the port is 1158 . https://prodb:1158/em/console/aboutApplication

2. Invoke emca command as below

./emca –reconfig ports -DBCONTROL_HTTP_PORT

STARTED EMCA at Oct 1, 2017 7:00:51 PM
EM Configuration Assistant, Version 11.2.0.3.0 Production
Copyright (c) 2003, 2011, Oracle.  All rights reserved.

Enter the following information:
Database SID: ecnmprod
Password for SYS user:

Do you wish to continue? [yes(Y)/no(N)]: Y
Oct 1, 2017 7:01:15 PM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at /oracle/app/oracle/cfgtoollogs/emca/prddb/emca_2017_10_01_19_00_51.log.
Oct 1, 2017 7:01:15 PM oracle.sysman.emcp.util.DBControlUtil stopOMS
INFO: Stopping Database Control (this may take a while) ...
Oct 1, 2017 7:01:37 PM oracle.sysman.emcp.util.DBControlUtil startOMS
INFO: Starting Database Control (this may take a while) ...
Oct 1, 2017 7:01:53 PM oracle.sysman.emcp.EMDBPostConfig performReconfiguration
INFO: Database Control started successfully
Oct 1, 2017 7:01:53 PM oracle.sysman.emcp.EMDBPostConfig performReconfiguration
INFO: >>>>>>>>>>> The Database Control URL is https://prddb:7100/em <<<<<<<<<<<
Enterprise Manager configuration completed successfully
FINISHED EMCA at Oct 1, 2017 7:01:53 PM

3. Check the status again:

./emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.4.0
Copyright (c) 1996, 2013 Oracle Corporation.  All rights reserved.
https://prdeaidb2:7100/em/console/aboutApplication
Oracle Enterprise Manager 11g is running.
------------------------------------------------------------------
Logs are generated in directory /oracle/app/oracle/product/11.2.0/dbhome_1/prddb/sysman/log

We have successfully changed the http port of the database console.