lftp with SSL (ftps) cannot run the ls command in Red Hat Enterprise Linux 5

Issue

• I'm trying to connect to a ftp server with lftp

lftp -c open -e "set ftps:initial-prot; set ftp:ssl-force true; set ftp:ssl-protect-data true; set ftp:ssl-allow off; ls -altr; " -u tester,testerpasswd ftps://xxx.xxx.xxx.xxx:990

But, after this command is executed, I got a hang with this output.

`ls -altr' at 0 [Making data connection...]