FTP reply code 110 is a preliminary response sent by the server during a file transfer restart. It includes a marker that the client can use to resume a transfer from a specific byte offset rather than starting over. This is part of the REST (restart) mechanism defined in RFC 959. The marker format is server-dependent but typically contains a byte offset. This code is relatively rare in modern FTP usage since most clients handle resume operations through the REST command followed by RETR or STOR, receiving the marker information through other means.
A previous file transfer was interrupted (network failure, timeout, or client disconnect) and the client is now resuming the transfer. The server sends 110 with a marker indicating the byte offset where the transfer can resume.
Some FTP server implementations send periodic restart markers during very large file transfers. These markers allow the client to resume from the last checkpoint if the transfer fails partway through.
Check that both the FTP client and server support the REST command for transfer resumption. Send FEAT to see if REST is listed in the server's feature set.
curl -v ftp://ftp.example.com/ -Q 'FEAT'
To resume a transfer, send REST with the byte offset before issuing RETR (download) or STOR (upload). The server will acknowledge with 350 and then begin the transfer from the specified offset.
curl -C - -O ftp://ftp.example.com/largefile.zip
If transfers are frequently interrupting, verify that your network path to the FTP server is stable and that no firewalls are prematurely closing idle data connections.
Scan PortsThe data connection is already established and the file transfer is beginning immediately.
The server is ready to transfer the file and is about to open the data connection.
The file transfer completed successfully and the data connection is being closed.
The data connection was closed unexpectedly and the file transfer was aborted.