The following commands are implemented.
   USER    EPRT    STRU    ALLO    DELE    SYST    RMD     MDTM
   PASS    EPSV    MODE    REST    CWD     STAT    PWD     PROT
   QUIT    LPRT    RETR    RNFR    LIST    HELP    CDUP    PBSZ
   PORT    LPSV    STOR    RNTO    NLST    NOOP    STOU    AUTH
   PASV    TYPE    APPE    ABOR    SITE    MKD     SIZE