Oracle_fdw not accessing Oracle database from Aurora PostgreSQL

Question

I'm trying to connect to an active Oracle database via oracle_fdw extension on Aurora PostgreSQL instance. The latest attempt at creating a server was:

CREATE SERVER foreign_oracle 
        TYPE 'Oracle12' 
        VERSION '12' 
        FOREIGN DATA WRAPPER oracle_fdw 
OPTIONS (dbserver '//xxx.xxx.xxx.xxx:1521/xxx');

After creating foreign table, select * on the table returns the following error, no matter how I format the connection string:

SQL Error [HV00N]: ERROR: connection for foreign table "oratab" cannot be established Detail: ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

Additional info:

• same Oracle db can be accessed with dbeaver/psql
• outbound rule for Aurora is set to everything
• I haven't tried using sqlplus because I want to avoid installing Oracle