How to resolve IO Error: The network adapter could not ... of sql developer AWS EC2

[root@ip-10-38-5-196 html]#systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2020-04-06 12:38:30 CDT; 2 days ago
     Docs: man:firewalld(1)
 Main PID: 3123 (firewalld)
   CGroup: /system.slice/firewalld.service
           └─3123 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Apr 06 12:38:30 ip-10-38-5-196 systemd[1]: Starting firewalld - dynamic firewall daemon...
Apr 06 12:38:30 ip-10-38-5-196 systemd[1]: Started firewalld - dynamic firewall daemon.
[root@ip-10-38-5-196 html]# systemctl stop firewalld
[root@ip-10-38-5-196 html]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Wed 2020-04-08 19:05:43 CDT; 3s ago
     Docs: man:firewalld(1)
  Process: 3123 ExecStart=/usr/sbin/firewalld --nofork --nopid $FIREWALLD_ARGS (code=exited, status=0/SUCCESS)
 Main PID: 3123 (code=exited, status=0/SUCCESS)

Apr 06 12:38:30 ip-10-38-5-196 systemd[1]: Starting firewalld - dynamic firewall daemon...
Apr 06 12:38:30 ip-10-38-5-196 systemd[1]: Started firewalld - dynamic firewall daemon.
Apr 08 19:05:42 ip-10-38-5-196 systemd[1]: Stopping firewalld - dynamic firewall daemon...
Apr 08 19:05:43 ip-10-38-5-196 systemd[1]: Stopped firewalld - dynamic firewall daemon.
[root@ip-10-38-5-196 html]# systemctl disable firewalld
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

Try again it should work. Assumption is your listener is up and has services registered. If not.

lsnrctl start listener

go to sql

alter system register;


Also assumption is if you have 12c or 19c you have the below parameters in sqlnet.ora listener and tnsnames based on your hostname IP, db name  and port configured mine as default 1521.

$ cat listener.ora
# listener.ora Network Configuration File: /u01/app/oracle/product/12.2.0.1/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.38.5.196)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )


$ cat sqlnet.ora
SQLNET.EXPIRE_TIME=2
SQLNET.ALLOWED_LOGON_VERSION_SERVER=11
#SQLNET.CRYPTO_CHECKSUM_SERVER=rejected
#SQLNET.ENCRYPTION_SERVER=rejected
DEFAULT_SDU_SIZE=1400


$ cat tnsnames.ora
# tnsnames.ora Network Configuration File: /u01/app/oracle/product/12.2.0.1/db_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

LISTENER_AWSDB =
  (ADDRESS = (PROTOCOL = TCP)(HOST = 10.38.5.196)(PORT = 1521))


AWSDB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.38.5.196)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = AWSDB)
    )
  )