ftp transfer problems - dropped data

  • Thread starter Thread starter Roger Dunn
  • Start date Start date
R

Roger Dunn

I have a customer who is using our software who is having problems
retrieving batches of files over ftp. (Our software has its own ftp
client code).

A review of the ftp log on our side shows it is dropping characters:

=== Log snippet =====
250 CWD command successful.
TYPE I
200 Type set to I.
PORT 172,16,1,33,83,226
200 PORT command successful.
RETR G2004-01-09_05-00-55_to_2004-01-10_04-08-25.dat
500 'TR G2004-01-09_05-00-55_to_2004-01-10_04-08-25.dat': command not
understood
======== End Snippet =====

You can see that it loses the 'RE' portion of 'RETR' when the server
echo's back the instruction. We have 1000's of customers who use our
software without problem so this is unique to his setup. I tried
making
delays between requests but that has not really helped. Any clues as
to
the dropped data?
 
Did you write the client or the server side?
Im assuming you're using tcp rather than udp, so your software should be
receiving the whole packet correctly.
Can only say go check for bugs in your parser or socket reading routines,
check that your buffers are thread safe etc Do you do any logging in your
functions?
 
There's not a bug in the software. (Read we have thousands of regular
users of this software and only 1 has the problem).

This is a hardware issue, but I am attempting to find out what
possible hardware related issue it could be.
 
There's not a bug in the software. (Read we have thousands of regular
users of this software and only 1 has the problem).

This is a hardware issue, but I am attempting to find out what
possible hardware related issue it could be.
Click to expand...

If you already know its a hardware issue, have you tried to isolate the
problem by changing out the hardware components one at a time to where the
isuue gets resolved. Then you'll know which hardware component is causing
the problem. And, if you already know its a hardware problem, why didn't
you tell us the configuration so that we could intelligently help you
troubleshoot?

You sound like many programmers. Blame the hardware before isolating the
problem. Maybe your program does not account for a specific hardware
configuration and therefore it is a software problem rather than a hardware
problem. For example, if your software does not work on Win2K with a 3com
NIC, is that a hardware problem or software problem? But we can't help
because you didn't provide any information as to why you think its a
hardware problem.
 
Hi Bob,
I don't believe it's feasible to check so deeply for hardware configurations
when you're on the firing end of programming windows. That would be an
enormous task. It should be up to the driver writer to get their act
together to be fully compliant with Windows standards.
As a programmer, I'm very sympathetic with bendedbeam. It's very difficult
when you get that one in several thousand where something just isn't
behaving like it should.
If it were a hardware problem, with knowledge of TCP, where is it logically
likely to occur?
 
The problem was found on the customer's end. He had some port
restrictions
and some weird round-robin ftp port assignment on his firewall. Some
of the packets that went through a valid port were ok, others not. He
opened the additional ports and his problem went away.

Here's a snippet of his firewall log:
======================================
2004/01/19 10:53:10 CST info src=208.144.4.253 dst=67.32.211.107
ipprot=6
sport=20 dport=18567 TCP SYN Packet Dropped
2004/01/19 10:53:16 CST Previous log entry repeated 1 times.
2004/01/19 10:54:05 CST info src=208.144.4.253 dst=67.32.211.107
ipprot=6
sport=20 dport=13736 TCP SYN Packet Dropped
2004/01/19 10:54:11 CST Previous log entry repeated 1 times.
2004/01/19 10:54:33 CST info src=220.73.165.140 dst=67.32.211.107
ipprot=1 icmp_type=3 icmp_code=3 ICMP Dest Unreachable, session
terminated
2004/01/19 10:54:36 CST Previous log entry repeated 2 times.
2004/01/19 10:54:39 CST info src=82.64.111.41 dst=67.32.211.107
ipprot=6
sport=4872 dport=135 Unknown inbound session stopped
2004/01/19 10:55:01 CST info src=208.144.4.253 dst=67.32.211.107
ipprot=6
sport=20 dport=10431 TCP SYN Packet Dropped
2004/01/19 10:55:07 CST Previous log entry repeated 1 times.
2004/01/19 10:55:38 CST info src=192.146.217.206 dst=67.32.211.107
ipprot=1 icmp_type=3 icmp_code=3 ICMP Dest Unreachable, session
terminated
=======================================
 
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