[REBOL] Re: Rebol and UDP
From: petr:krenzelok:trz:cz at: 26-Nov-2000 12:44
----- Original Message -----
From: Holger Kruse <[holger--rebol--com]>
To: <[rebol-list--rebol--com]>
Sent: Sunday, November 26, 2000 3:07 AM
Subject: [REBOL] Re: Rebol and UDP
> On Sun, Nov 26, 2000 at 02:31:13AM +0100, Petr Krenzelok wrote:
> > REBOL
> > would have to store packet identifiers in a block somewhere in port
object
> > structure, till you read out related data out of the buffer. Hmm, now as
I
> > think about it - without such functionality, UDP implementation in REBOL
is
> > pretty useless then, no? Holger?
>
> No, see my other mail. The UDP protocol carries identifiers in the
payload,
> not in the header. The UDP header only contains port numbers, length and
> checksum, no ID.
I read it already, thanks for the explanation ...
> > Also - port/state/flags doesn't seem to be "real" IP datagram flag
> > representation (SYN,ACK,URG,FIN,RST)
>
> Confusion, confusion... :-)
>
> SYN,ACK,URG,FIN,RST are TCP flags, not IP (or UDP) flags. They are used
> internally within the TCP/IP stack, never exported via APIs.
>
Ah, we just downloaded some net-monitor from ethereal.com and are wondering
at all the info OS throws at us :-) You are, of course, right - above
functionality is part of TCP layer. I learned one more thing about
connections - although our Scenix stack inexpectably FINed connection, we
were able to throw data at the chip and it WAS received. Then I read
something about so called "half closed" connections. It's interesting -
although server closed connection, we were able to throw more data to it -
it was just ignored at the data processing level, or so it seems to me ...
confusion, confusion :-)
> UDP does not have any flags in its header at all.
Hmm, well, I never looked so deep inside, - although our Scenix chip TCP
stack claims it supports UDP, it just receives data and UDPProcPktIn has
just one line - return :-) ... kind of great support = do it yourself :-)
What's more - I was confused as my friend told me, we could use UDP for
image transfer, store all packetIDs, then process all the number and get
back to our device asking for certain missing fragments (packets) of image
data received ....
> IP does have flags in its header, but they are used to reassemble IP
> fragments (within the TCP/IP stack) only, and are not useful at the
> application level. The stack processes them by itself anyway.
>
> port/state/flags is an internal field that indicates the mode of operation
> at the REBOL port level. It is used to indicate things like "direct",
> "binary", "lines" mode etc., and is also used to store some temporary
> state. Those parts of port/state/flags which are useful for applications
> are exported via the soon-to-be-documented get/set-modes API.
great. Is there anything more left to be advanced at the REBOL protocol
level after we will get async root-protocol? :-) Or are we just near
protocol nirvana? :-)
Thanks,
-pekr-
