You can also use tnsping utility on command prompt to check Oracle Net connectivity. Follow these steps to check the connection to particular SID.
Open Command prompt.
Write tnsping < SID for the database connectivity you want to check >
If you get the message “Used TNSNAMES adapter to resolve the alias” then tnsping utility is able to resolve the service name.
If you get “TNS-03505: Failed to resolve name” message then tnsping utility is not able to resolve the service name and you need to check the SQLNET.ora and TNSNAMES.ora files on your machine.