Use domain name to connect to embedded Apache FtpServer

Question

I'm trying to set up a simple test FTPS server in Java using Apache FtpServer and connect to it using a domain name instead of the IP address.

I've pointed the A record to the IP address and set up the SSL certificate. Based on the Apache FtpServer documentation, here is what my code looks like so far:

        FtpServerFactory ftpServerFactory = new FtpServerFactory();
        ListenerFactory listenerFactory = new ListenerFactory();
        listenerFactory.setPort(990);
        listenerFactory.setServerAddress("example.com");

        SslConfigurationFactory sslConfigurationFactory = new SslConfigurationFactory();
        sslConfigurationFactory.setKeystoreFile(JKS);
        sslConfigurationFactory.setKeystorePassword(JKS_PASS);
        listenerFactory.setSslConfiguration(sslConfigurationFactory.createSslConfiguration());
        listenerFactory.setImplicitSsl(true);

        ftpServerFactory.addListener("default", listenerFactory.createListener());

        PropertiesUserManagerFactory userManagerFactory = new PropertiesUserManagerFactory();
        userManagerFactory.setFile(USERS_PATH.toFile());

        BaseUser test = new BaseUser();
        sample1.setName("test");
        sample1.setPassword("test");
        sample1.setHomeDirectory(HOME.getAbsolutePath().toString());
        test.setAuthorities(List.of(new WritePermission());

        UserManager userManager = userManagerFactory.createUserManager();
        try {
            userManager.save(test);
        }
        catch (FtpException e) {
            e.printStackTrace();
        }

        ftpServerFactory.setUserManager(userManager);

        FtpServer server = ftpServerFactory.createServer();
        try {
            server.start();
        }
        catch (FtpException e) {
            e.printStackTrace();
        }

However, when I try to connect to the FTPS server, I get an ECONNREFUSED - Connection refused by server from my FTPS client.

Are there any steps that I missed?

Answer 1

If your client reports a 'connection refused' that usually indicates (no guarantee) that no firewall prevented the TCP traffic, the connection request ended up on the intended machine but nothing was accepting the connection on the port you tried to connect to.

Things you can check: Was the server process running? Was the server process on the correct port? Did the client connect to the correct port?

You might try to connect with another client (e.g. curl) just to see whether the TCP connection can be established. You might try to connect to another port (e.g. 22 / ssh) to see if the client can establish the connection.