The oracle client must be installed with PLSQL Developer

To use PLSQL Developer, you must install the oracle client, because you need to configure the relevant content on the client side to use PLSQL Developer.

Configuration method:

1. Find the tnsnames.ora file in the $ORACLE_HOME/client_1/network/admin directory and open it in text mode.

2. Add the following:

local instance name =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = database IP address) (PORT = port number))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = service name)
    )
  )

3. Log in with the tool.