- From: Robert Sayre <sayrer@gmail.com>
- Date: Thu, 26 Jan 2006 21:58:29 -0500
- To: www-archive@w3.org
Routing Atom Entries through Google Talk Servers
Google Talk uses the IETF standard XMPP (aka Jabber) as its
instant-messaging protocol. XMPP is open and XML-based, so it's easy
to extend. In fact, it's so open that servers generally don't care
what's contained in a message envelope. Instead of a typical XMPP IM
message, we'll show how to send Atom Entry documents as XMPP payloads.
This demo will use the Google Talk server, but any XMPP/Jabber server
will do.
How it Works
To illustrate this capability, we'll need two scripts--one to send the
XMPP message and one to recieve it. The scripts send and receive
messages that would normally be handled by IM client programs. As of
this writing, it isn't common for XMPP clients to include Atom
parsing, but expect that to change.
Python provides all that we'll need to accomplish this, with the
exception of an XMPP module. Not to worry, the xmpp module provides
everything required. Instead of the mainstream xmpp module, these
scripts use the version provided by Gajim, a PyGTK IM client. The
Gajim version is more actively maintained, and includes several fixes
for the SASL/TLS features required by Google Talk.
First off, we'll tackle sending the XMPP messages. We start by by
importing the required modules and declaring some constants (change
these to addresses and passwords for your accounts).
import sys,xmpp
# Google Talk constants
FROM_GMAIL_ID = "sender@gmail.com"
GMAIL_PASS = "secret"
GTALK_SERVER = "talk.google.com"
TO_GMAIL_ID = "recipient@gmail.com"
Our client has to connect and authenticate, just like any other IM
client. We connect though 5222, the standard XMPP port. Fortunately,
the xmpp.Client.auth method takes care of all the SASL/TLS negotiation
under the covers.
jid=xmpp.protocol.JID(FROM_GMAIL_ID)
cl=xmpp.Client(jid.getDomain(),debug=[])
if not cl.connect((GTALK_SERVER,5222)):
raise IOError('Can not connect to server.')
if not cl.auth(jid.getNode(),GMAIL_PASS):
raise IOError('Can not auth with server.')
Preparing an Atom Entry to send is pretty easy, thanks to some
convenience functions provided by the xmpp module. For demonstration
purposes, we'll just parse a string.
sample_entry = '''
<entry xmlns="http://www.w3.org/2005/Atom">
<title>My First Post</title>
<author>
<name>John Doe</name>
</author>
<content type="text">Contents of my post</content>
<updated>2003-10-23T18:35:51Z</updated>
<link
href="http://example.com/weblog/2003/10/my_first_post.html" />
<id>tag:typepad.com,2003:post-3</id>
</entry>'''
entry_node = xmpp.simplexml.XML2Node(sample_entry)
All that's left to do for the sending script is push our entry to the
recipient, and then disconnect.
message=xmpp.Node('jabber:client message',
attrs={'to':TO_GMAIL_ID},
payload=[entry_node])
cl.send(message)
cl.disconnect()
The resulting XMPP payload looks like this:
<message xmlns="jabber:client"
to="recipient@gmail.com" from="sender@gmail.com/C3B772CF">
<entry xmlns="http://www.w3.org/2005/Atom">
<title>My First Post</title>
<author>
<name>John Doe</name>
</author>
<content type="text">Contents of my post</content>
<updated>2003-10-23T18:35:51Z</updated>
<link href="http://example.typepad.com/weblog/2003/10/my_first_post.html" />
<id>tag:typepad.com,2003:post-3</id>
</entry>
</message>
If this XMPP message is sent to a normal XMPP client, it will probably
be ignored, since the payload isn't something expected. That's OK,
because it's easy to hook up a listening client to the Google Talk
server as well. The constants are pretty similar to the sender script:
import sys,xmpp
# Google Talk constants
GMAIL_ID = "recipient@gmail.com"
GMAIL_PASS = "secret"
GTALK_SERVER = "talk.google.com"
The receiving script will need to stay running, waiting for messages
to arrive. The step and loop functions just run endlessly, while the
messageHandler function will be called whenever a message comes in
from the network.
def messageHandler(conn,mess_node):
print "Message From:",mess_node.getFrom()
print mess_node.getChildren()[0]
def step(conn):
try:
conn.Process(1)
except KeyboardInterrupt: return 0
return 1
def loop(conn):
while step(conn): pass
After executing some connection and authentication code identical to
what's required by the sender script, we instruct the xmpp.Client to
execute messageHandler function whenever there's an incoming message.
cl.RegisterHandler('message',messageHandler)
We then send a message to the server alerting it to our presence. This
is what's sent when an account is online, and how the server knows
it's ok to send the client messages from others.
cl.sendInitPresence()
Lastly, we'll print a message so it's clear everything has gone
smoothly, enter the loop we set up earlier, and wait for something to,
um, Talk to us.
print "Google Talk Client started."
loop(cl)
The Complete Listing
send script
#!/usr/bin/python
# Be sure to use the XMPP module from
# http://trac.gajim.org/browser/trunk/src/common/xmpp/
# as it contains many patches not present in the
# mainstream version
import sys,xmpp
# Google Talk constants
FROM_GMAIL_ID = "sender@gmail.com"
GMAIL_PASS = "secret"
GTALK_SERVER = "talk.google.com"
TO_GMAIL_ID = "recipient@gmail.com"
jid=xmpp.protocol.JID(FROM_GMAIL_ID)
cl=xmpp.Client(jid.getDomain(),debug=[])
if not cl.connect((GTALK_SERVER,5222)):
raise IOError('Can not connect to server.')
if not cl.auth(jid.getNode(),GMAIL_PASS):
raise IOError('Can not auth with server.')
sample_entry = '''
<entry xmlns="http://www.w3.org/2005/Atom">
<title>My First Post</title>
<author>
<name>John Doe</name>
</author>
<content type="text">Contents of my post</content>
<updated>2003-10-23T18:35:51Z</updated>
<link
href="http://example.com/weblog/2003/10/my_first_post.html" />
<id>tag:typepad.com,2003:post-3</id>
</entry>'''
entry_node = xmpp.simplexml.XML2Node(sample_entry)
message=xmpp.Node('jabber:client message',
attrs={'to':TO_GMAIL_ID},
payload=[entry_node])
cl.send(message)
cl.disconnect()
recieve script
#!/usr/bin/python
# Be sure to use the XMPP module from
# http://trac.gajim.org/browser/trunk/src/common/xmpp/
# as it contains many patches not present in the
# mainstream version
import sys,xmpp
# Google Talk constants
GMAIL_ID = "recipient@gmail.com"
GMAIL_PASS = "secret"
GTALK_SERVER = "talk.google.com"
def messageHandler(conn,mess_node):
print "Message From:",mess_node.getFrom()
print mess_node.getChildren()[0]
def step(conn):
try:
conn.Process(1)
except KeyboardInterrupt: return 0
return 1
def loop(conn):
while step(conn): pass
jid=xmpp.protocol.JID(GMAIL_ID)
cl=xmpp.Client(jid.getDomain(),debug=[])
if not cl.connect((GTALK_SERVER,5222)):
raise IOError('Can not connect to server.')
if not cl.auth(jid.getNode(),GMAIL_PASS):
raise IOError('Can not auth with server.')
cl.RegisterHandler('message',messageHandler)
cl.sendInitPresence()
print "Google Talk Client started."
loop(cl)
Running The Code
First, we'll start the receiving script in one prompt.
prompt1% python receive_atom.py
Google Talk Client started.
In a second prompt, we'll send the Atom Entry. This prompt could be
anywhere, since the message is being routed through Google's servers.
prompt2% python send_atom.py
That script will exit quickly, and we should see the entry that's been
sent pop up in the first prompt...
prompt1% python receive_atom.py
Google Talk Client started.
Message From: sender@gmail.com/C3ABB5D7
<entry xmlns="http://www.w3.org/2005/Atom">
<title>My First Post</title>
<author>
<name>John Doe</name>
</author>
<content type="text">Contents of my post</content>
<updated>2003-10-23T18:35:51Z</updated>
<link href="http://example.typepad.com/weblog/2003/10/my_first_post.html" />
<id>tag:typepad.com,2003:post-3</id>
</entry>
Hacking the Hack
The scripts in this hack are pretty simple, but Atom can carry lots of
payloads, and can come from anywhere. The sender could pull entries
down from the Web, or the receiver could post the entries using the
Atom Publishing Protocol. Also, XMPP allows the exchanges to happen a
lot faster than the typical 1/2 hour intervals in syndication, so all
sorts of more time-sensitive uses are possible.
Network Working Group R. Sayre
Internet-Draft January 26, 2006
Expires: July 30, 2006
2-Way RSS
draft-sayre-2-way-rss-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
This document may not be modified, and derivative works of it may not
be created.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 30, 2006.
Abstract
This memo presents a protocol that uses XML and HTTP to publish and
edit Web resources.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. The 2-Way RSS Model . . . . . . . . . . . . . . . . . . . . . 3
4. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Listing . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Authoring . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. 2-Way RSS Feeds . . . . . . . . . . . . . . . . . . . . . . . 6
8. 2-Way Media RSS Feeds . . . . . . . . . . . . . . . . . . . . 7
9. Service Outlines . . . . . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
11. Security Considerations . . . . . . . . . . . . . . . . . . . 11
12. Informative References . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
2-Way RSS uses HTTP [RFC2616] and XML [W3C.REC-xml-20040204] to
publish and edit Web resources.
2. Notational Conventions
[@@ 2-Way RSS namespace docs]
The terms 'URI' and 'IRI' are shorthand for the identifiers specified
in [RFC3986] and [RFC3987].
3. The 2-Way RSS Model
2-Way RSS uses HTTP to operate on collections of Web resources
represented by RSS feeds [RSS]. This section illustrates the editing
cycle for RSS items.
o GET is used to retrieve an item or perform a read-only query.
o POST is used to create a new, dynamically-named item.
o PUT is used to update an existing item.
o DELETE is used to remove an item.
4. Discovery
To discover the location of the feeds exposed by a 2-way RSS service,
the client must locate and request the Service Outline, an OPML
document.
Client Server
| |
| 1.) GET Service Outline URI |
|------------------------------->|
| |
| 2.) Service OPML Document |
|<-------------------------------|
| |
1. The client sends a GET request to the Service Outline URI.
2. The server responds with an OPML Document containing the
locations of feeds provided by the service. The content of this
document can vary based on aspects of the client request,
including, but not limited to, authentication credentials.
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5. Listing
Once the client has discovered the location of a feed in the outline,
it can request a listing of the feed's items. However, a feed might
contain an extremely large number of items, so servers are likely to
list a small subset of them by default.
Client Server
| |
| 1.) GET to RSS Feed URI |
|------------------------------->|
| |
| 2.) 200 OK, RSS Feed Doc |
|<-------------------------------|
| |
1. The client sends a GET request to the RSS Feed's URI.
2. The server responds with an RSS Feed Document containing a full
or partial listing of the feed's membership.
6. Authoring
After locating a feed, a client can add entries by sending a POST
request to the feed; other changes are accomplished by sending HTTP
requests to each item.
6.1. Create
Client Server
| |
| 1.) POST Item to Feed URI |
|------------------------------->|
| |
| 2.) 201 Created @ Location |
|<-------------------------------|
| |
1. The client sends an RSS item to the server via HTTP POST. The
Request URI is that of the RSS Feed.
2. The server responds with a response of "201 Created" and a
"Location" header containing the URI of the newly-created RSS
item.
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6.2. Read
Client Server
| |
| 1.) GET or HEAD to Item URI |
|------------------------------->|
| |
| 2.) 200 OK RSS Item |
|<-------------------------------|
| |
1. The client sends a GET (or HEAD) request to the item's URI.
2. The server responds with an RSS item.
6.3. Update
Client Server
| |
| 1.) PUT to RSS Item URI |
|------------------------------->|
| |
| 2.) 200 OK |
|<-------------------------------|
| |
1. The client PUTs an updated RSS item to the item's URI.
2. The server responds with a successful status code.
6.4. Delete
Client Server
| |
| 1.) DELETE to Item URI |
|------------------------------->|
| |
| 2.) 204 No Content |
|<-------------------------------|
| |
1. The client sends a DELETE request to the item's URI.
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2. The server responds with successful status code.
6.5. Success and Failure
HTTP defines classes of response. HTTP status codes of the form 2xx
signal that a request was successful. HTTP status codes of the form
4xx or 5xx signal that an error has occurred, and the request has
failed. Consult the HTTP specification for more detailed definitions
of each status code.
7. 2-Way RSS Feeds
7.1. GET
RSS feeds can contain extremely large numbers of items. A naive
client such as a web spider or web browser would be overwhelmed if
the response to a GET contained every item in the feed, and the
server would waste large amounts of bandwidth and processing time on
clients unable to handle the response. As a result, responses to a
simple GET request represent a server-determined subset of the items
in the feed.
An example 2-Way RSS feed:
<rss>
<channel>
<title>The Baron in the Trees</title>
<link>http://example.org/trees.html</link>
<description>Recent posts.</description>
<!-- 0 or more item elements follow -->
<item>
<title>Chapter One</title>
<description>It started out simple...</description>
<guid>uuid:941e12b4-6eeb-4753-959d-0cbc51875387</guid>
<link>http://example.org/chapter1.html</link>
<pub:edit href="./item7.rss"/>
</item>
</channel>
</rss>
Each member item is represented by an <item> element, but those items
are not an editable representation of the each item. To retrieve the
source representation of the item, clients send a GET request to the
URI found in each item's [@@ TBD XX pub:edit element. Derived
resources are located by examining an item's r:link elements]
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7.2. POST
A 2-Way RSS feed also accepts POST requests. The client POSTs a new
item to the RSS feed. Some feeds only accept POST requests with
certain media-types, so a POST request could result in a response
with a status code of 415 ("Unsupported Media Type"). In the case of
a successful creation, the status code is 201 ("Created").
Example HTTP request creating a new item in a feed:
POST /dilettante HTTP/1.1
Host: example.org
User-Agent: Cosimo/1.0
Content-Type: application/rss+xml
Content-Length: nnnn
<item>
<title>Chapter One</title>
<description>It started out simple...</description>
<guid>uuid:941e12b4-6eeb-4753-959d-0cbc51875387</guid>
<link>http://example.org/chapter1.html</link>
<pub:edit href="./item7.rss"/>
</item>
Example response.
HTTP/1.1 201 Created
Date: Mon, 21 Mar 2005 19:20:19 GMT
Server: CountBasic/1.0
ETag: "4c083-268-423f1dc6"
Location: http://example.org/items/foo13241234.xml
8. 2-Way Media RSS Feeds
The items within 2-way Media RSS Feeds do not represent uniform types
of content. For example, they might contain podcasts, JPEG images,
text documents, MPEG movies, or any other type of resource the server
allows.
8.1. GET
2-Way Media RSS Feeds return an RSS feed much like the textual 2-Way
RSS feeds described above, but with a few additions. The entries
also contain an <enclosure> element with a 'url' attribute pointing
to the media object. This URL can be used to edit the uploaded media
object, using PUT and DELETE. Such items may contain edit links used
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to edit the item metadata.[@@TBD As with any RSS item, related and
derived resources can be located by inspecting an item's r:link
elements.]
An example 2-Way Media RSS Feed:
<rss>
<channel>
<title>My Pics</title>
<link>http://example.org/pics</link>
<description>Recent photos.</description>
<!-- 0 or more item elements follow -->
<item>
<title>beach25</title>
<link>http://example.org/beach-pic1.html</link>
<guid>uuid:941e12b4-6eeb-4753-959d-0cbc51875387</guid>
<description>This was awesome.</description>
<enclosure url="http://example.org/beach.tiff"
length="15234"
type="image/tiff" />
</item>
</channel>
</rss>
Implementations require that each such item contain either a <title>
or <description> element. The value for the <title> element will
likely be provided by the client, as a way for users to associate
their local objects with those they have uploaded to the server (see
POST below).
8.2. POST
To add an item to a 2-Way Media RSS feed, clients POST the resource
to the Media feed's URL. Clients should provide a 'Title' request
header to provide the server with a short string identifying the
object to users. Clients may include a 'Content-Description' header
[RFC2045] providing a more complete description of the content. In
addition, servers may inspect the POSTed entity for additional
metadata to be exposed in an <item> element when listed in a 2-Way
Media RSS feed. For example, the server might inspect a JPEG file
for EXIF headers containing creator data.
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An example request:
POST /pics HTTP/1.1
Host: example.org
User-Agent: Cosimo/1.0
Content-Type: image/tiff
Content-Length: nnnn
Title: A Trip to the beach
Content-Description: It was so fun.
...binary data...
An example response:
HTTP/1.1 201 Created
Date: Mon, 21 Mar 2005 19:20:19 GMT
Server: CountBasic/2.0
ETag: "4c083-268-423f1dc6"
Location: http://example.org/stuff/beach.tiff
[@@TBD deal with response ambiguity]
9. Service Outlines
Many 2-Way RSS applications require a basic resource layout in order
to ease configuration requirements. Servers use Service Outline OPML
documents to convey information about related groups of 2-Way RSS
feeds. On a blogging service, for example, each group might
represent a distinct blog and associated resources.
Example Service Outline document:
<opml version="1.1">
<head>
<title>My Blogs</title>
</head>
<body>
<outline text="Pretending to be Excited" type="rss"
xmlUrl="http://example.org/pretend.rss"/>
<outline text="Quick Links" type="rss"
xmlUrl="http://example.org/side.rss"/>
</body>
</opml>
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Servers are not required to expose a Service Outline OPML document,
but experimental deployment experience has shown that a single
document which signals some basic information about the server's
configuration can greatly simplify client implementations. The
simplest useful Service Outline OPML document shows the location of a
single feed:
<opml version="1.1">
<head>
<title>Flickr</title>
</head>
<body>
<outline text="My Pics" type="rss"
xmlUrl="http://example.org/pics.rss"/>
</body>
</opml>
If another 2-Way RSS feed is added, the document can be upgraded to
reflect that.
<opml version="1.1">
<head>
<title>Flickr</title>
</head>
<body>
<outline text="Pics" type="rss"
xmlUrl="http://example.org/pics.rss"/>
<outline text="Overwraught Prose" type="rss"
xmlUrl="http://example.org/blog.rss"/>
</body>
</opml>
Finally, more extensive services could require some amount of
hierarchical grouping.
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<opml version="1.1">
<head>
<title>Flickr</title>
</head>
<body>
<outline text="Pics" type="rss"
xmlUrl="http://example.org/pics.rss"/>
<outline text="Crazy Delicious">
<outline text="Overwraught Prose" type="rss"
xmlUrl="http://example.org/blog.rss"/>
<outline text="Still More Overwraught Prose" type="rss"
xmlUrl="http://example.org/blog2.rss"/>
</outline>
</body>
</opml>
9.1. Categories
[@@ tbd]
10. IANA Considerations
[@@ fill out for application/rss+xml and application/opml+xml]
11. Security Considerations
[@@TBD]
12. Informative References
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Author's Address
Robert Sayre
Email: rfsayre@boswijck.com
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Sayre Expires July 30, 2006 [Page 13]
Received on Friday, 27 January 2006 08:55:24 UTC