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I need to download large files from an FTP server running ProFTPD. The server is not mine, all I can do if some problems occur is to contact its admin. And the problem is as follows.

First, I connect to the server in passive mode and download starts. Then, after a while, connection may become lost, and ftp-client (not actually important which one, because I used many, the latest one is Download Master) tries to reconnect. The server is configured to limit number of connection from a single IP. And at that moment server returns an error stating that the limit is exceeded. This looks like ProFTPD does not feel that previous connection has been dropped or does not process it.

Is this normal? To my knowledge of TCP I'd say, that the server should get a socket disconnected event somehow. If so, is it possible to configure the ProFTPD in such a way that dropped connections will be handled properly and promptly?

I asked the question to that server's admin, but he says it's not possible.

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up vote 2 down vote accepted

It depends on the way the connection is "lost". The server only notices it when the client explicitly shuts down the TCP connection (either with FIN or RST packets). But if the client reconnects due to a timeout (when network problems cause all packets to be lost), it might be that the server hasn't noticed that yet – and has no way of noticing unless it periodically pings the client, or closes the connection after a timeout.

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