"lftp" on RHEL6 fails to connect to vsftpd on RHEL7

I have configured vsftpd on RHEL7 and i am trying to transfer data to it using lftp from RHEL6. lftp seems to fail after sending the PASS command for anonymous login. ---> USER anonymous PASS xxxxxx **** gnutls_record_recv: An unexpected TLS packet was received. ---- Closing control socket cd: Fatal error: gnutls_record_recv: An unexpected TLS packet was received. The corresponding vsftpd log message: Wed Mar 18 08:20:41 2020 [pid 37007] FTP command: Client "XX.XXX.XX.XX", "USER anonymous" Wed Mar 18 08:20:41 2020 [pid 37007] [anonymous] FTP response: Client "XX.XXX.XX.XX", "331 Please specify the password." Wed Mar 18 08:20:41 2020 [pid 37007] [anonymous] FTP command: Client "XX.XXX.XX.XX", "PASS " Wed Mar 18 08:20:41 2020 [pid 37006] [cfgdb] OK LOGIN: Client "XX.XXX.XX.XX", anon password "xxxxxx" But the same lftp works when connecting to a vsftpd configured on RHEL6. vsftpd logs from RHEL6 on successful connection: Wed Mar 18 06:16:26 2020 [pid 706] FTP command: Client "XX.XXX.XX.XX", "USER anonymous" Wed Mar 18 06:16:26 2020 [pid 706] [anonymous] FTP response: Client "XX.XXX.XX.XX", "331 Please specify the password." Wed Mar 18 06:16:26 2020 [pid 706] [anonymous] FTP command: Client "XX.XXX.XX.XX", "PASS " Wed Mar 18 06:16:26 2020 [pid 703] [cfgdb] OK LOGIN: Client "XX.XXX.XX.XX", anon password "xxxxxx" Wed Mar 18 06:16:26 2020 [pid 709] [cfgdb] FTP response: Client "XX.XXX.XX.XX", "230 Login successful." lftp version on RHEL6: # lftp -v LFTP | Version 4.0.9 | Copyright (c) 1996-2010 Alexander V. Lukyanov vsftpd on RHEL7: # vsftpd -v vsftpd: version 3.0.2