Re: FTP from one website to another?
- From: "clintonG" <csgallagher@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Sat, 24 Jun 2006 12:17:31 -0500
Kevin, you've been a real gem over the years. Your response provides me with
helpful information and insight I'm sure you gained through much painful
trial and error. I'll get right into it...
<%= Clinton
"Kevin Spencer" <uce@xxxxxxx> wrote in message
news:uonigr5lGHA.4064@xxxxxxxxxxxxxxxxxxxxxxx
Hi Clinton,
Clearer than mud! ;-)
Okay, assuming that we're talking about an XML file generated by a web
application (websiteA), and assuming that websiteB is hosted on a web
server that shares the directories with an FTP server on serverB, it
should not be a problem, except for possible security (firewall) issues.
If using .Net platform 2.0, you can use the System.Net.FtpWebRequest and
System.Net.FtpWebResponse classes to upload the file from websiteA to the
FTP server on websiteB.
I'm not crazy about these 2 classes (even though they work pretty well),
as they mimic the behavior of HttpWebRequest and HttpWebResponse, even
though under the covers, so to speak, they are doing something entirely
different, such as maintaining an opened Connection. I suppose this was a
decision by some Microsoft designer or architect who figured having 2
distinctly different behavior models might confuse our pretty little
heads. But as you know, I'm all about personal responsibility, and believe
that software should have a programming interface that behaves the way it
does. If the developer understands nothing about the underlying protocol,
he/she needs to before he/she starts writing code. I'm all for
productivity tools, but enhancing productivity and enabling laziness and
willful ignorance are 2 entirely different things, with 2 entirely
opposite values.
The HttpWebRequest and HttpWebResponse classes are designed specifically
to work in and mimic the stateless "single Request/Response" model of
HTTP. The FtpWebRequest and FtpWebResponse classes are designed to work in
a connected client/server Session, but to behave as if they are working in
a stateless "Single Request/Response" situation, which they are not
working in. For this reason, if you understand much about FTP, the object
model is counter-intuitive. Of course, if you're an ignoramous, it seems
perfectly logical. But heaven help you if things don't work the way you
expect, because being an ignoramous, you will not know why, or what to do
about it!
In particular, downloading files with th FtpWebRequest class is not hard
at all, but uploading them is somewhat cryptic. The reason? To upload a
file, you must create a Network Stream, and write the file to it, after
agreeing with the server on the port to send the stream to. This is all
carefully hidden in the FtpWebRequest class, and if something goes wrong,
due to the object model, it's awfully hard to figure out what. In many
cases, it works without any issues at all. In a few, you're in deep
trouble.
This is why I ended up writing my own FTP client socket-based classes that
mirror the behavior of an actual FTP session, and can even log the entire
message exchange, as well as socket-related information. But that isn't
going to help you any at this point!
That said, they do the job. You may need to read a few articles to help
you learn how to use them:
http://blogs.msdn.com/adarshk/archive/category/7225.aspx
http://blogs.msdn.com/adarshk/archive/2004/09/13/229069.aspx
http://geekswithblogs.net/mikeymac/archive/2006/03/10/71990.aspx
In addition, here are a few pointers:
Most FTP servers that allow file uploads require a login. Be sure to use
NetworkCredentials with your FtpWebRequest to make sure that it logs in
with the correct credentials.
The key to uploading is in the FtpWebRequest.GetRequestStream method. This
encapsulates the messaging that is exchanged to set up the port to send to
on the remote server. The NetworkStream returned is actually pointing to
the Stream Socket that will be written to.
You will want to convert your XML document to a stream to upload it.
Use Passive FTP mode to ensure that firewall issues are minimized (long
story).
Be aware of potential firewall issues. FTP uses 2 connections for
uploading and downloading. Port 21 on the remote server is not likely to
be an issue, but could be. However, your client will attempt to use other
ports to transfer data. This is why you use Passive mode, since if the
client on this side of the firewall specifies a port, most firewalls will
allow incoming connections on that port.
I think that's about it. Be sure to come back if you have any problems.
--
HTH,
Kevin Spencer
Microsoft MVP
Professional Chicken Salad Alchemist
I recycle.
I send everything back to the planet it came from.
"clintonG" <csgallagher@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:eAS3h4vlGHA.3924@xxxxxxxxxxxxxxxxxxxxxxx
Hello Kevin,
Thanks for the smedumacation ;-) I've never written any code that used
FTP. The concern here is ease of use and trying to provide a seamless
transition for a user on websiteA who will be using an application on
websiteA that will output an XML file that needs to be located somewhere
under the root of the user's website that I refer to as websiteB.
When the application on websiteA that generates the XML file is finished
doing so the application will ask the user if they want to see the XML
file in the browser to allow them to copy-paste or use File Save As to
save to their local file system. If they want to use a local instance of
FTP to transport the file to their website (websiteB) so be it -- or --
if possible -- the application will ask the user to select a means to
login to websiteB from websiteA and use the application running on
websiteA to transport the file to websiteB.
I've never gotten close to any task like this. Is it clear as mud?
<%= Clinton
"Kevin Spencer" <uce@xxxxxxx> wrote in message
news:%23B9hZwulGHA.2204@xxxxxxxxxxxxxxxxxxxxxxx
Hi Clinton,
Yes, under the correct circumstances. Forgive me if I tell you anything
you already know, as I don't know what you already know, so I'm going to
start at a comfortably low position and work my way up from there...
A web application is an application designed to run in a web server. A
web server is a server application that communicates with its clients
via HTTP (HyperText Transfer Protocol). This is a text-based messaging
protocol which runs on a TCP transport over the Internet, which sends
text messages back and forth between client and server, and can also be
used to transmit binary data as well.
FTP (File Transfer Protocol) is another text-based protocol that runs on
a TCP transport over the Internet. It also involves a server (an FTP
server) and multiple clients, which transmit requests and responses in
text format, and can be used to transmit both text and binary data
between server and client.
There are several differences between these 2 protocols. FTP is a
"connected" protocol. It maintains an open connection between the client
and the server (on the server port 21 usually) for the duration of a
user session. This "command connection" is used to exchange the requests
and responses between server and client, and separate connections are
created on different ports as needed to transfer files. HTTP is a
"disconnected" protocol, which can be configured to keep the underlying
TCP connection opened, or close it and reopen it with each
request/response. Because of the "disconnected" nature of HTTP, it is
stateless. It only uses a single port (usually Port 80) to transfer all
messaging and data. FTP is older than HTTP, and has several issues with
firewalls and security that HTTP does not, but both are generally pretty
reliable, as TCP is a reliable networking protocol. They use entirely
different text "languages" to communicate. And of course, although it is
theoretically possible to create an FTP client that can render HTML, and
use FTP as the underlying protocol, FTP is not used for this purpose,
and is generally regarded as simply a mechanism for transferring files 2
ways between client and server, whilt HTTP is generally regarded as a
one-way protocol in which the client is generally only receiving files
from the server.
Enough of that. Now down to the nitty gritty of what you were asking.
Both protocols require a server to listen and handle incoming client
requests. Both protocols can run on the same machine, and can work with
the same directories. So, it is quite possible, and even common for an
HTTP web to have FTP access. Many web designers use FTP to upload their
files to the web server. So, the only real question you need to ask is,
does the web server machine have an FTP server with access to the same
files and folders as the web site? If so, an application can use both
FTP and HTTP to exchange data and files between server and client.
--
HTH,
Kevin Spencer
Microsoft MVP
Professional Chicken Salad Alchemist
I recycle.
I send everything back to the planet it came from.
"clintonG" <csgallagher@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:%23zGox$slGHA.3588@xxxxxxxxxxxxxxxxxxxxxxx
I'm puzzled and don't think this is possible but if an application that
is running on websiteA generates a file can FTP be used from websiteA
to transfer that file to websiteB which would be located on another
server?
--
<%= Clinton Gallagher
NET csgallagher AT metromilwaukee.com
URL http://www.metromilwaukee.com/clintongallagher/
.
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