D-Link DLS-2750U ftp firmward update

220 Ftp firmware update utility
421 Login incorrect.
421 Login incorrect.

HTTP/1.1 200 OK
Content-Length: 23
Content-Type: text/html; charset=UTF-8
Connection: close

HTTP/1.1 401 Unauthorized
Content-Length: 0
WWW-Authenticate: Digest realm="IgdAuthentication", domain="/", nonce="OGY1YzQ4NTU6M2FlNThkNTM6MjFkZGNiYzY=", qop="auth", algorithm=MD5, opaque="5ccc09c403ebaf9f0171e9517f40e41"