pi@VallrunElmeter ~/Counter $ sudo ./ftpupload 
Local file size: 99 bytes.
* About to connect() to 192.168.0.151 port 21 (#0)
*   Trying 192.168.0.151...
* connected
* Connected to 192.168.0.151 (192.168.0.151) port 21 (#0)
* FTP 0x1d49430 state change from STOP to WAIT220
< 220 ProFTPD 1.3.3g Server (NETGEAR ReadyNAS) [192.168.0.151]
> USER anonymous
* FTP 0x1d49430 state change from WAIT220 to USER
< 331 Anonymous login ok, send your complete email address as your password
> PASS WS_DATA1
* FTP 0x1d49430 state change from USER to PASS
< 230 Anonymous access granted, restrictions apply
> PWD
* FTP 0x1d49430 state change from PASS to PWD
< 257 "/" is the current directory
* Entry path is '/'
* FTP 0x1d49430 state change from PWD to STOP
* protocol connect phase DONE
* DO phase starts
> CWD WS_DATA
* FTP 0x1d49430 state change from STOP to CWD
< 250 CWD command successful
> EPSV
* FTP 0x1d49430 state change from CWD to PASV
* Connect data stream passively
< 229 Entering Extended Passive Mode (|||33440|)
*   Trying 192.168.0.151...
* connected
* Connecting to 192.168.0.151 (192.168.0.151) port 33440
* FTP 0x1d49430 state change from PASV to STOP
* DO phase is complete
> TYPE I
* FTP 0x1d49430 state change from STOP to STOR_TYPE
< 200 Type set to I
> STOR ws_data2.txt
* FTP 0x1d49430 state change from STOR_TYPE to STOR
< 150 Opening BINARY mode data connection for ws_data2.txt
* FTP 0x1d49430 state change from STOR to STOP
* DO-MORE phase ends with 0
*** We read 99 bytes from file
* We are completely uploaded and fine
* Remembering we are in dir "WS_DATA/"
< 226 Transfer complete
> RNFR ws_data2.txt
< 350 File or directory exists, ready for destination name
> RNTO ws_data3.txt
< 250 Rename successful
> APPE ws_data.txt
< 425 Unable to build data connection: Invalid argument
* QUOT string not accepted: APPE ws_data.txt
* Connection #0 to host 192.168.0.151 left intact
* Quote command returned error
curl_easy_perform ()  failed: Quote command returned error
> QUIT
* FTP 0x1d49430 state change from STOP to QUIT
< 221 Goodbye.
* FTP 0x1d49430 state change from QUIT to STOP
* Closing connection #0