I installed Oracle XE 18c on RHEL on my laptop, got it configured, created connections with two applications (DBeaver and DbVisualizer) as well as able to connect with sqlplus. It all worked "perfectly".
This morning, I had to "IT Crowd" reboot my laptop (turned it off and back on again), then started Oracle XE using sqlplus, accessed a table to confirm the engine actually came up although the appropriate startup messages were generated.
My problem is neither of the DB apps (above) can connect to the XE database again. I've checked the listener.ora file, it matches the connection configuration in both applications for the hostname and port number. The /etc/hosts file still contains the same configuration.
Note that the server is configured in listener.ora to listen on port 1539.
The message I get from both apps when I "ping the server" is effectively the same: "
Cannot connect to '<redacted>' on port 1539
along with the standard "please check and try again" advice. I can't find any log files with entries for today. It sounds trite, but none of the configuration files changed, the only difference I can see is having rebooted and possibly something did not "stick", perhaps a process did not get started.
Please accept my thanks in advance.