No 226 Transfer complete on large files

Question

When downloading a large file (860M), I did not get the 226 Transfer complete at the end of the transfer so the transfer is stuck at the end. For small files, there was no problem.
This was tested with the Simple WinForm FTP Client.

Comments

What is the FTP server you are communicating with?
Is a proxy involved in the communication?
Can you please set logging level to Debug (can be set on Connection window) and send it to support@rebex.net for analysis?

Answer 1

The log showed that the server did not respond with any command on control connection. This might be a common issue where a router or firewall drops the FTP control connection that stays inactive during the transfer. To address that, try enabling the keep-alive option:

ftp.Settings.KeepAliveDuringTransfer = true;
ftp.Settings.KeepAliveDuringTransferInterval = 60; // send NOOP every 60 seconds