Angus Robertson - Magenta Systems Ltd wrote:
>> I guess that won't make a difference, since if a port were
>> still in use an exception in Listen/Bind should be raised
>> and CommandPASV() should return the error.
> There is a table in the server which keeps track of which passive
> ports are in use, although it won't help if another application is
> using the port.

This concept and the fact that passive listening sockets are
created dynamically when a range is used may be a weak point,
though that must not be the problem here. 

Btw: Serv-U opens one persistent listening socket per port in the
range on startup, thus once they are listening no subsequent
probs. with ports in use can happen. 

>> Isn't it possible that winsock refuses the connection attempt due
>> to a full ListenBacklogQueue
> Unlikely, these are Windows 2000 servers running IIS/5 FTP for five
> years or so (and FileZilla) without any problems, I've only just
> changed one to use ICS FTP server now it has mode z.
> Looking at more logs, I see:
> '501 Cannot RETR. Error - Connection reset by peer (#10054)' and
> '501 Cannot RETR. Error - Connection aborted (#10053)' errors
> are coming back as well for passive downloads.  But they usually work
> on the next attempt.

Can you reproduce those errors in a simple environment that uses 
plain TCP/IP connections? Later today I will try as well.

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