Hi
I hope someone can point me in the right direction to understand some
behaviour we have seen regarding ftpserver.
Our ftpserver is configured to listen on 1.2.3.4:9021, with passive
ports 9020, 9021 and this may be the source of our problem.
Looking though the log file we found that one client was allocated port
9020 upon a PASV request but for some reason did not transmit data and
hence release it, so when a second client came in and requested a PASV
port he got 9021from which he started transmitting data. We believe at
that time a third client tried to establish a connection but was
refused. After about a minute the first client terminated its session
(connection was forcibly closed by the remote host type of exception was
recorded) and released port 9020 (since it was used later in another
client session).
So I guess my first question is that if all PASV ports are in use and
the listening port happens to be a port specified in the passive ports
range, what do you expect when another client tries to connect to ftpserver?
A follow up question: is it possible for a client to "lock" a port?
--
Regards
Peter
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