[JDEV] File transfers

Thu Jun 6 21:23:21 CDT 2002

I don't understand the arbitrary port comment... They are arbitrary.
Marshall and others picked em, and that was that.  When I hit the send
button in my email client (Outlook) it connects to exchange on some god
awful port with some god awful protocol that is most definitely not 110 and
is most definitely not SMTP (SMTP is 25 by the way, not 110).  Now there's a
connector that plugs into exchange and sends my message out to the
appropriate SMTP server via port 25, but that has nothing to do with POP
unless the other end HAPPENS to be using POP as the mailbox access
mechanism.  That POP server on the other end in some ways acts as a client
to the SMTP server, although not via networked protocols but via file system
semantics or whatever the particular package has decided the right way to
communicate between components is (e.g. on Win2k simple SMTP server, I would
just look in the mailroot\Mailbox directory, or use the CDO "client" objects
to access the mail store from a POP server I could write).

POP, HTTP, SMTP and most modern protocols are really nothing special.  I
could implement a POP "server" on my "client machine" pretty damn easily,
and could pretty much reuse the same code for an HTTP "server" on my client.
This would blur the lines in the case where, for example, I wrote a local
POP proxy.  From the point of view of Outlook Express, my POP proxy is the
server, but from the distant POP server it is the client. The fact that all
of these protocols are text based, fixed command set protocols blurs the
importance of clients and servers because of exactly what you say, that a
client asks and a server answers.  This is not a component-wide or "process"
wide distinction necessarily, it is a REQUEST wide decision, and any or all
components can make requests of each other.  This is why it is generally a
good idea to implement file transfer by having the client act like an HTTP
"server".  #1, it's easy, and #2, if it really IS a full blown web server
(i.e. for a firewall workaround) everything still works just the same.

This is all turning into a conceptual argument, and clearly you're not going
for the analogy/metaphor, which is fine.  I can't speak for Mike, but I
certainly don't need any lessons in Internet protocols, I've been here since
there weren't any.  In one paragraph I think you're saying you want to make
client-server into peer-to-peer/client-client.  If I'm understanding you
right, I totally agree.  And what I understand that to mean is that these
labels of distinction really aren't relevant.  So the question comes down to
what components are well suited to doing what tasks.  The Jabber server is
not well suited architecturally to act as a byte repeater for client
non-messaging data transfer.  I'm not sure I'd want to do anything to
encourage this just so some client developer can be lazy about implementing
things the right way.  (Not to mention that this is actually complex to
implement in ADDITION to a proper file transfer mechanism, and in the end
costs our poor client developers more time, not less)

I trust the maturity and experience of the members of this list to be able
to understand conceptual discussions of this nature, this isn't developer
school.  The original discussion was about whether the Jabber "server"
should be used to shuttle packets on behalf of clients and whether that
should be part of the protocol, at this point I'm confused reading your mail
whether you advocate this or don't.  I'll be clear, I do not advocate
creating protocol elements to allow the concept of a "file" to be routed,
split, encoded, and reassembled by Jabber servers.  I advocate a mechanism
for negotiating protocol based multi-party "connections" (i.e. clients
providing endpoints) for things like file transfer, video conferencing,
networked full-motion-video Parcheesi, and whatever the heck else the
developer community thinks up.  Whatever mechanism is used should not use
the words "file transfer" in anything but string literals in my opinion.

-----Original Message-----
From: Mike Oliver [mailto:ollie at appsaspeers.com]
Sent: Thursday, June 06, 2002 8:34 PM
To: jdev at jabber.org
Subject: RE: [JDEV] File transfers

oh, right and ports 25, 143 and 110 are arbitrary.

At 04:50 PM 6/6/2002 -0700, you wrote:

He knows what he's talking about, he's just assuming too much in his
descriptions.  People who don't know what they're talking about don't use
words like MTA and MUA, and if they do they act very proud of knowing it. :)

Hard distinctions between client and server are SOOO last century. :)  

Geez and I thought last century was just a couple of years ago.

>From a conceptual perspective, a *local* POP server (i.e. mycompany.com) is
in some ways a client for the overall server "cloud" of Internet mail.  SMTP
is essentially a non-realtime store and forward network, which is "batch" in
many ways, for lots of good reasons.

Are we in La La land?  You name me one email server that uses something
other than SMTP to transfer internet Mail between servers?  When you hit
that old send button you tell your email client to open good old server port
110 and transfer the email message and attachments via SMTP (the P stands
for Protocol and there is no N for Network in it) and your email server
looks at the addresses and sends copies of the message to all the addresses
it can find or to another SMTP server that might know more addresses, which
in turn sends all the messages off to other SMTP servers...POP is the
protocol for email clients to retrieve the email and attachments from a
SERVER as is IMAP with the key difference being the ability to have a
persistent store of folders/mailboxes.  POP is NOT used any other way.  So
your conceptual local POP server NEVER acts as a client and accesses some
other server in the "cloud", it sits there patiently until some other
'server' sends it something.

So from the cloud of smoke you two must be smoking conceptually, you can't
make client-server, into client-client OR peer to peer.  Those are words you
know as well, but knowing their meaning is more important.   A client makes
requests and a server answers them.  Yes indeed it gets cloudy when a server
talks to a server and the roles blur on a request by request basis, but not
the protocols they use.   

I am not advocating use of SMTP for Jabber File Transfers, however a mix of
Protocols that are accepted protocols for file transfers and messaging is
what I think we all want.  The Jabber protocol IS NOT a good idea for large
files, but some direct client to client or peer to peer mechanism IS a good
idea.

Maybe I am being to precise and too concise for you two.  But as an
Architect and developer it IS important and since this is a developer's
forum I choose not to mislead those that may be beginning to confuse them
with some "concepts" that are simply WRONG.

Knowing the words is only half the battle knowing what they mean takes a
little more effort.

And those points of view are part of the reason we both think that putting
this special "realtime non-messaging packet forwarder" hat on the Jabber
server is a stretch, and has all the problems we've previously mentioned. 

-----Original Message----- 

From: Mike Oliver [ mailto:ollie at appsaspeers.com
<mailto:ollie at appsaspeers.com> ] 

Sent: Thursday, June 06, 2002 7:38 PM 

To: jdev at jabber.org 

Subject: RE: [JDEV] File transfers

Ok adding value, you simply don't know what you are talking about.

How's that?  POP AND IMAP are protocols for Clients to talk to Servers to
access stores of messages and attachments.  A Pop or IMAP Client DOES NOT
talk to another Pop or IMAP Client...EVER...SMTP is the way you SEND
messages to those stores and every single email message you send is
transferred using SMTP and BTW SendMail is just an SMTP Program for sending
mail, it has nothing to do with "bulk".  Have you ever setup an email
client?  If you did you had to setup the email server for getting your email
and choose POP3 or IMAP4 and then an SMTP server for outgoing, or if you
leave that blank it tries to use the same server you setup for incoming.
But these are on different ports even if on the same ip address/dns name.

If YOU want to add value, don't spout about things you obviously know
NOTHING about.  Read the specifications about POP3, IMAP4 AND SMTP and you
can find those at http://www.ietf.org <http://www.ietf.org/> 

I completely agree it depends on where you are standing and you are standing
in the dark. 

At 02:06 PM 6/6/2002 -0700, you wrote:

Mike cogently queries: 

> What planet are you from?  

There's a great way to add value to a thread. :) 

> POP, IMAP and MAPI (Exchange) ARE NOT "client-to-client", PLEASE! 

Sure, why not?  user --> sendmail --> mail spool accessible via POP, 

at which point the server stops being so much of a server and starts 

acting a little more like a peer (POP, IMAP and MAPI being ad hoc, 

connected, conversational programs, unlike SMTP, which is largely a 

batch-oriented bulk drop).  It all depends where you're standing. 

No need to question my mudball of origin. 

> sendmail is just an SMTP mail transfer agent program and no different than

> any other SMTP mail transfer agent program like those from Netscape and 

> Microsoft...ARG! 

Netscape makes an MTA?  What's it called?  I've seen their MUA, but 

I'm surprised to hear they have an MTA.  I bet it crashes a lot. :) 

F. 

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Michael Oliver
Chief Technology Officer
AppsAsPeers.com
7391 S. Bullrider Ave.
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