Cannot connect to database hosted at CentOS VM through SQL Developer on Windows I've installed Oracle 12c smoothly today and was able to start lsnrctl and database.
SQL*Plus connection is okay inside VM.
I've set the IP address to be static @ 192.168.0.20 (CentOS VM).

I am able to ping the VM address from Windows but I cannot connect to the database through SQL Developer inside Windows. This is the error I got:


  The network adapter is unable to establish the connection


I suspect it may be a firewall problem? But I have opened port 1521 using firewall-cmd.
try to setting listener, for example

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.20)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )   
  )  


tnsname

DBORACLE =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.20)(PORT = 2001))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = dboracle)
    )
  )