ios - How to change the working directory in iPhone programatlically(FTP) -

i trying establish ftp connection ftp server in ios (authentication based). maintain login status listing directory , if directory listing count 0 login unsuccessful.

now problem whenever log in root directory "romfs" shown in screen shot in red circle , want directory access other directory @ same level highlighted in red rectangle. directly set url directory proper username/ password.

    ----"ftp://server_ip/ahci02:2/db/"  

but trying list \romfs folder question how change working directory "romfs" "ahci02:2" programmatically in ios.

thnx in advance.

pgggyyyyy