Re: Socket problem using linux as server
Re: Socket problem using linux as server
- Subject: Re: Socket problem using linux as server
- From: "Justin C. Walker" <email@hidden>
- Date: Sat, 26 Nov 2005 17:32:20 -0800
On Nov 23, 2005, at 10:43 , Per Jespersen wrote:
I have a problem with a test server/client application, that I have
made using BSD sockets. If I run my server on OS X 10.4, and my
client on the same, everything works fine, whether I listen on
loopback or on '*', and whether my client connects on loopback or
actual IP address. But if I try to run server on a linux server and
client on MAC, and my connection is NAT'ed, the checksum in my send
packages are wrong according to ethereal. This is the case whether
I listen on the MAC or on the linux. Does anyone have any ideas?
P.s. sorry if this has already been answered earlier, but I was
not able to get the search to work, and browsing through years of
postings seemed to be a major task :-)
I will guess that you are seeing a red herring. If ethereal is
running on a system, like most recent Mac OS X variants, that
supports checksum off-loading (so packets in memory are tagged with
an indicator telling the stack to avoid computing checksums), it will
appear that the checksums are wrong. However, the NIC will be doing
the checksum computation before sending (or after receiving), so
what's "on the wire" is correct.
You can tell whether this is the case by looking at one TCP
connection. If the connection is acknowledged, and data flows, the
checksums are fine. If the sender continues to send the same SYN
packet, or the receiver continues to receive it without acknowledging
it, then you may have a problem.
My suspicion is that there is something else going wrong, and
probably in the subtle differences between the BSD and Linux view of
the sockets API.
Regards,
Justin
--
Justin C. Walker, Curmudgeon-At-Large
Institute for General Semantics
--------
If you're not confused,
You're not paying attention
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