Re: Tcp header

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Additionally : just ready function to calculate checksum you can take from
http://groups.google.co.il/group/microsoft.public.win32.programmer.networks/browse_thread/thread/5098805b862859f0/9ed558794b39caba?lnk=st&q=arkadyf+checksum+header&rnum=1#9ed558794b39caba
Arkady

"Alexander Nickolov" <agnickolov@xxxxxxxx> wrote in message
news:uH49ZEqrHHA.5032@xxxxxxxxxxxxxxxxxxxxxxx
You are wrong. All accepted sockets share the port of the
listening socket, in this case port 80. I suspect you are confusing
with ephemeral ports at the client.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Ronny" <ronny@xxxxxxxxxxx> wrote in message
news:eEPcttnrHHA.4180@xxxxxxxxxxxxxxxxxxxxxxx
thanks,
Some other beginner question-
As I understand, in a common scenario, the Http server accepts a new TCP
connection on a new socket. The port (of the new socket) shouldn't be 80
but something different.
1. How can I know the port and see it with the Ethereal sniffer?
2. Why do I see the original Http port(80) in the packets coming from the
client even after establishing the connection and not the new expected
port?

Thanks

Ronny


1. How to calculate the Check Sum?

Checksum: 16 bits

The checksum field is the 16 bit one's complement of the one's
complement sum of all 16 bit words in the header and text. If a
segment contains an odd number of header and text octets to be
checksummed, the last octet is padded on the right with zeros to
form a 16 bit word for checksum purposes. The pad is not
transmitted as part of the segment. While computing the checksum,
the checksum field itself is replaced with zeros.


2. Is there some reference that describes the tcp fields and values?


You can find all this in the RFC 793 (Transmission Control Protocol)
http://www.faqs.org/rfcs/rfc793.html



OK?
br GP








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