Re: bug in java.net.Socket??
Thomas Pornin wrote:
If the SYN packet was emitted then, by definition, the client code (the
Java code which creates a Socket instance) is fine and does what it is
told. The server should respond with a ACK+SYN packet. If that packet
does not come back, then either the _server_ has a bug, or (more
probably) some firewall went in the way of the packets, dropping either
the client-sent SYN or the server-sent ACK+SYN.
FTP passive mode usually entails choosing a random port, contrary to
active FTP where a well-known port is used. Firewalls seldom approve of
random ports.
horos wrote:
No.. [sic] I've controlled for all of this:
1. Regular, vanilla ftp works (passively, on the same box, connecting
to the same server, same user and password).
2. The perl wrapper Net::FTP works (passively on the same box,
connecting to the same server, same user and password).
3. The interface worked before in its assigned function (doing vanilla
ftp - the underlying API is j-ftp), and had worked for about a year.
It just stopped working.
In fact, I've automated the testing so that the same passive port
(which is randomly generated) comes up in both Net::FTP and the java
API version. Net::FTP works with the assigned port (and gets an
established connection, as well as vanilla FTP), the java [sic] API version
doesn't. The only thing that makes sense is that the SYN_SENT packet
being sent somehow differs between Socket APIs.
I suppose the next step would be testing a different java [sic] ftp client,
and see if I can replicate the behavior with this other client. I'm
welcome as to suggestions for this - what are some good java [sic]-based ftp
clients?
I'll bet you ten bucks it's not a bug in the API but in your code.
This is the time for an SSCCE.
<http://sscce.org/>
--
Lew
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