在 Oracle 19c Java 存储过程中使用 java.nio 出现问题

Question

I'm trying to connect to my localhost kafka server from java function saved into Oracle database 19.3. The problem is that i cannot reach the server. In database trace files i see that kafka library is using java.nio package to connect to server. Any connection attempt is ending with "Connection refused". I admit also that I can send data to topics from command line tool.

To check if my requests from database are incoming to localhost server at port 9092 i have run Hercules TCP Server and setup it to listen on this port. Then when i'm using my java function it nothing happens. I write some "test" functions to make only simple connection to my local server, to see if there is some network problem. The function where i use java.net package is working and i can see that i receive connection requests from database, but the function where i use java.nio package is returning always "Connection refused"

I have granted java.net.SocketPermission to my database user:

exec dbms_java.grant_permission( 'KAFKA', 'SYS:java.net.SocketPermission', '*', 'connect,resolve' );
commit;

Are there needed some special permissions to use java.nio package into oracle database java functions or maybe i'm doing something wrong?

Here are my java "test" functions code:

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED "testTCP" AS
import java.net.Socket;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;

public class testTCP {

    public static String conn_nio(){
        
        String response;
        try {
            InetSocketAddress hostAddress = new InetSocketAddress("localhost", 9092);
            SocketChannel client = SocketChannel.open(hostAddress);
            client.close();
            response = "OK";
        }
        catch(Exception e){
            response = "Message: " + e.getMessage() + " Cause: " + e.getCause();
        }
        return response;
    }

    public static String conn_net() {
        String response;
        try
        {
            Socket socket = new Socket( "localhost", 9092 );
            socket.close();
            response = "OK";
        }
        catch( Exception e )
        {
            response = "Message: " + e.getMessage() + " Cause: " + e.getCause();
        }
        
        return response;

    }

}

Answer 1

Cannot reproduce. I pointed it to port 8080 of a local HTTP server which I started with

python -m SimpleHTTPServer 8080

and both connection methods are ok:

CREATE OR REPLACE FUNCTION test_net RETURN VARCHAR2 AS
LANGUAGE JAVA NAME 'testTCP.conn_net() return java.lang.String';
/

CREATE OR REPLACE FUNCTION test_nio RETURN VARCHAR2 AS
LANGUAGE JAVA NAME 'testTCP.conn_nio() return java.lang.String';
/

SELECT test_net FROM DUAL;
OK

SELECT test_nio FROM DUAL;
OK