File Service Protocol (FSP) Frequently Asked Questions [Part 2/2]

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A. J. Doherty

Jul 24, 1995, 3:00:00 AM7/24/95
Archive-name: fsp-faq/part2
Last-modified: 1995/07/21
Version: 1.0
Frequency: Twice Monthly


Section 3: Technical Issues

Q.3.1 What are the main differences between FSP and FTP? How does FSP work?

From the user's point of view, the differences are not that great, except that
some of the more annoying features of FTP are gone. Here are the main

* The protocol can stand things going down: if the server or the network
falls over in the middle of a transfer, you can just wait until it comes
back up. You don't have to reconnect, and even better, if the server went
down 90% through grabbing a file, you can continue from where you left

* The protocol doesn't need a username or password. You just throw packets
at the server. You don't have to identify yourself (though you're not
completely anonymous -- see below).

* It's harder to kill off a site with an FSP server than with an FTP server.
The FSP daemon is designed to be as lightweight as possible: it doesn't
fork off any sub-processes, and it takes steps to limit the amount of
traffic it handles.

* The user interface is completely different. The interface that comes with
the package consists of eleven commands that you can call from the shell.
In effect, your shell is providing all the nice functions like command
line editing. This makes the interface much more versatile than FTP's.
(See below for how to get an FTP-like interface, though).

* FSP is a bit slower than FTP. This is a feature, not a bug. The point is
to keep the communication lightweight, and not to flood the net.

From the programmer's point of view, fsp is a complete rewrite.

* Instead of TCP sockets, it uses datagrams to communicate, so that the
connection doesn't break on a flaky line.

* FTP works by opening a port, and then asking the server to send a file to
it. FSP uses the same port all the time for communication, and asks for
segments of a file. So you can start off a transfer half way through a
file, if you really want to.

* The server tries to make sure you don't ask for packets too quickly. Each
packet it sends out has a random identification number, which the client
must return on the next request. (If the client loses the number, it must
wait a few seconds before the server accepts another packet from it).
Therefore, the client has to wait for an answer to each request before it
sends out the next one.


Q.3.2 How secure/anonymous is FSP?

By default, the FSP daemon keeps logs of transactions, along with their site
names. An FSP administrator could use this to find out who you are, with a
reasonable degree of certainty.

In short, FSP gives you no more privacy than anonymous FTP. Anyone who tells
you different has a less devious mind than most FSP admins I know.

Why not make FSP more anonymous? Well, it's impossible to make a protocol with
complete anonymity, since at some point, the remote site will have to send a
file back to you, and it needs at least an address to send it to.

If you really need privacy, you can encrypt any files you make available, and
only give out the decryption password to a select few. But of course, you have
to trust them to keep the password safe.


Q.3.3 Why not add passwords to FSP?

Thanks to Joseph Traub for the material for this section)

* They don't add much security. If you use one password for the whole site,
then you might just as well set up the site and only tell a few people its
port number. That's no more or less secure than using a password. Besides,
it's easier just to set up the server only to respond to certain hosts.

* Any other password system is likely to be a big lose on efficiency, since
you'll have to check every single packet.

* The main use of server passwords appears to be so that people can move
pirated software around, and the authors don't want to add code to support

* This capability does NOT belong in FSP because it gets away from the
concept of lightweight simple file transfers.


Q.3.4 So what *does* FSP stand for?

As of 12th August 1993, FSP stands for `File Service Protocol'. Thanks to
Michael Grubb ( for the words, and Wen-King for the initials.

Other suggestions were:

* File Slurping Protocol
* Flaky Stream Protocol
* FTP's Sexier Partner


Section 4: Who's Who?

Q.4.1 Who writes and maintains FSP software?

Unix Versions:
The current maintainer (as of March 1994) is Andy Doherty
(, who also maintains the alt.comp.fsp FAQ and
wrote and maintains FSPtool an X-Windows FSP client.

The previous maintainers were Phil Richards ( and Pete
Bevin ( from July 1993 to March 1994. Phil is
also the maintainer of fspclient, an FTP-like interface for FSP.

Joseph Traub (was was maintainer from Dec 1992 to July
1993 (versions 2.6.5 to 2.7.1).

Wen-King Su ( wrote the original Unix version
(versions 1.0 to 2.6.4).

Sven Pechler ( wrote and maintains a VMS version.

OS/2 is handled by Larkin Lowrey (

Lindsey Smith, of the MS-DOS rewrite is


Q.4.2 Who writes and maintains FSP Client Software?

Jim Browne ( and Modris Berzonis ( are both
writing (soon to be released?) Macintosh clients. See Section 2.2.3.

Andy Doherty ( wrote and maintains 'FSPtool' an
X-Windows based Unix client. Also the FSP and alt.comp.fsp FAQ maintainer.

Ian Heath ( wrote 'winfsp' an MS-Windows based client.

Nicolai Langfeldt's ( wrote and maintains 'fspcli' a Perl based

Ove Ruben R Olsen ( wrote and maintains 'fspsh', another Perl
based client.

Phil Richards' ( wrote and maintains 'fspclient'.


Q.4.3 Who helped put this FAQ together?

The following people have contributed to the FAQ. Thanks very much to all of

* Pete Bevin (
* Tony Brannigan (
* Jim Browne (
* Dan Charrois (
* Wilson Cheung (
* Maurizio Codogno (
* David DeSimone (
* Ian Dickinson (
* Andy Doherty (
* Ian Heath (
* Jan Nicolai Langfeldt (
* Larkin Lowrey (
* Ove Ruben R Olsen (
* Jerome Pier (j...@edu.unl.unlinfo)
* Lutz Prechelt (
* Phil Richards (
* Lindsey Smith (
* Wen-King Su (
* Joseph Traub (


Section 5: Site Information

Q.5.1 What FSPable sites exist ?

The following is a small list of the some sites sites which are available
through the FSP protocol. This list should be reasonably up to date but comes
with no warranty. It is in the unofficial "taxus" format. is
the official home for FSP software distributions, most packages can be found
there. 21 genie / # small UK site 2001 germany / # big German archive (FSP) 6969 luth / # Top of Europe 21 src / # SUNsite Northern Europe 21 terra / # big Netherlands site 21 wu / # lots of mirrors ...

For more site information sources see Q.2.3

Comments and suggestions should be sent to The
information in this FAQ is in no way associated with the University of Reading
or its Information Technology Unit. This FAQ represents the efforts of many
people to help consolidate information about FSP. There is no guarantee that
the information in this FAQ is correct, nor can anyone contributing to this FAQ
be held responsible for the information they provide.

Addresses in () after the answer are the email addresses of people who have
contributed. Please let me know if you don't wish to be identified when you

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