Errata

When trying to connect to this example, I got an exception:

SSHDemoAvatar instance has no attribute 'eofReceived'

According to the source at http://twistedmatrix.com/trac/browser/tags/releases/twisted-8.2.0/twisted/conch/interfaces.py the ISession interface also needs eofReceived and windowChanged, in addition to the ones already in the example.

Note from the Author or Editor:
This interface has probably changed since the book was published. The code should be updated, but I don't have the resources to work on it currently.

The sentence "The third class, WordCountProxy client, contains..."
should read "The third class, WordCountProxyClient, contains..."

Note from the Author or Editor:
Correct, this should be changed as noted above.

Hi,

I am not sure whether this is really an error but I find that Example 4-6 modified for PostgreSQL and the psycopg2 database adapter crashes the python 2.5 interpreter unless I replace runQuery with runOperation.
Using the later, I get a working example with the following diff output from the original:

$diff databaseblog.py databaseblog.py.orig
2c2
< from twisted.enterprise import adbapi
---
> from twisted.enterprise import adbapi, util as dbutil
4,18c4,9
< #import psycopg2
<
< # This code depends on a pre-existing PostgreSQL table
< # created with the following SQL schema:
< #
< #CREATE TABLE posts(
< # post_id serial unique,
< # title varchar(255) NOT NULL,
< # body text,
< # primary key (post_id)
< # );
<
<
< DB_DRIVER = "psycopg2"
< DB_ARGS = "dbname=postgres host=localhost user=postgres password=mytestdb2"
---
> DB_DRIVER = "MySQLdb"
> DB_ARGS = {
> 'db': 'test',
> 'user': 'abe',
> 'passwd': 'gear42',
> }
82,84c73,77
< query = "insert into posts (title, body) values ('%s', '%s')" \
< % (title, body)
< self.db.runOperation(query).addCallback(
---
> query = """
> Insert into posts (title, body) values (%s, %s)
> """ % (dbutil.quote(title, "char"),
> dbutil.quote(body, "text"))
> self.db.runQuery(query).addCallback(
88c81
<
---
>
108c101
< dbConnection = adbapi.ConnectionPool(DB_DRIVER, DB_ARGS)
---
> dbConnection = adbapi.ConnectionPool(DB_DRIVER, **DB_ARGS)

Note from the Author or Editor:
This appears to be correct.

In paragraph 2, lines 2 and 3, both references to /formhandler
should be /posthandler.

This change is also needed to be consistent with the code in Example 4-3 and with the URL portrayed in Figure 4-5.

Note from the Author or Editor:
Confirmed - it should say 'posthandler', not 'formhandler'.

The sentence ending in "send the form data to the page formhandler using an HTTP POST request" should read "send the form data to the page posthandler using an HTTP POST request".

This is also evident from the URL shown in the browser output of Figure 4-5 and from the code listing.

Note from the Author or Editor:
Confirmed - it should say 'posthandler', not 'formhandler'.

"from connectiontester import testConnect"

should be

"from connectiontest import testConnect"

Inside Example 2-6 dataforward.py, the second line is::

from twisted.protocols import basic

However, basic is not used anywhere in the example.

Note from the Author or Editor:
Good catch. That import statement can be removed.

The code printed in the book is out of date. The code in the current example code zip already fixes this problem.
The new code is listed below:

from twisted.internet import reactor, protocol
from twisted.protocols import basic

class EchoProtocol(basic.LineReceiver):

def connectionMade(self):
print "Connection from", self.transport.getPeer().host

def lineReceived(self, line):
if line == 'quit':
self.sendLine("Goodbye.")
self.transport.loseConnection()
else:
self.sendLine("You said: " + line)

class EchoServerFactory(protocol.ServerFactory):
protocol = EchoProtocol

if __name__ == "__main__":
port = 5001
reactor.listenTCP(port, EchoServerFactory())
print "Server running, press ctrl-C to stop."
reactor.run()

SHould read:
"This means that when the result of client.downloadPage comes in, the
reactor will call returnFilename with the result of client.downloadPage
as the first argument and the filename as the second argument."

<title>Form Test</html>
when it should read -
<title>Form Test</title>

The text reads, "MyRequestHandler uses SetHeader to set the Content-Type header to text/html"... However, this call to SetHeader
doesn't appear anywhere in the example code on page 41!

This paragraph should read:
The Request class also provides a setHeader method for adding headers to
the response. For example, you can use setHeader to add a Content-Type
header indicating the type of content in the response body.
setHeader('Content-Type', 'text/plain') would generate the HTTP header
Content-Type: text/plain, telling the browser that the response is plain
text. If you don't manually set a Content-Type header, the Request class
will default to sending the Content-Type for HTML documents, text/html
(as it does when you run Example 4-2).

Here is the updated code to replace the example in the book:

from twisted.web import resource, static, server

class ColorPage(resource.Resource):
def __init__(self, color):
self.color = color

def render(self, request):
return """
<html>
<head>
<title>Color: %s</title>
<DEFANGED_link type='text/css' href='/css/styles.css' rel='Stylesheet' />
</head>
<body DEFANGED_STYLE='background-color: #%s'>
<h1>This is #%s.</h1>
<p DEFANGED_STYLE='background-color: white'>
<a href='/colors/'>Back</a>
</p>
</body>
</html>
""" % (self.color, self.color, self.color)

class ColorRoot(resource.Resource):
def __init__(self):
resource.Resource.__init__(self)
self.requestedColors = []
self.putChild('', ColorIndexPage(self.requestedColors))

def render(self, request):
# redirect /colors -> /colors/
request.redirect(request.path + '/')
return "Please use /colors/ instead."

def getChild(self, path, request):
if path not in self.requestedColors:
self.requestedColors.append(path)
return ColorPage(path)

class ColorIndexPage(resource.Resource):
def __init__(self, requestedColorsList):
resource.Resource.__init__(self)
self.requestedColors = requestedColorsList

def render(self, request):
request.write("""
<html>
<head>
<title>Colors</title>
<DEFANGED_link type='text/css' href='/css/styles.css' rel='Stylesheet' />
</head>
<body>
<h1>Colors</h1>
To see a color, enter a url like
<a href='ff0000'>/colors/ff0000</a>. <br />
Colors viewed so far:
<ul>""")
for color in self.requestedColors:
request.write(
"<li><a href='%s' DEFANGED_STYLE='color: #%s'>%s</a></li>" % (
color, color, color))
request.write("""
</ul>
</body>
</html>
""")
return ""

class HomePage(resource.Resource):
def render(self, request):
return """
<html>
<head>
<title>Colors</title>
<DEFANGED_link type='text/css' href='/css/styles.css' rel='Stylesheet' />
</head>
<body>
<h1>Colors Demo</h1>
What's here:
<ul>
<li><a href='/colors'>Color viewer</a></li>
</ul>
</body>
</html>
"""

if __name__ == "__main__":
from twisted.internet import reactor
root = resource.Resource()
root.putChild('', HomePage())
root.putChild('colors', ColorRoot())
styles = resource.Resource()
styles.putChild('styles.css', static.File('styles.css'))
root.putChild('css', styles)
site = server.Site(root)
reactor.listenTCP(8000, site)
reactor.run()

The return value references the URI /colors/, while the rest of the code uses
/color/.

Note from the Author or Editor:
The code should be updated to use /colors/ instead of /color/, as per the screenshots and descriptions.

This requires the following changes:

in ColorRoot.render:
# redirect /colors -> /colors/

In ColorIndexPage.render:
<a href='/colors/ff0000'>/colors/ff0000</a>. <br />

in HomePage.render:
<li><a href='/colors/'>Color viewer</a></li>

The table describes styles.css as being available under /css/styles.css, when in
fact it is at /styles.css.

Note from the Author or Editor:
This is correct. It should be /styles.css. In addition, the previous table item "/css, virtual resource for holding css stylesheets", is invalid and should be removed.

In example 5-1, the opening "<body>" tag in IndexPage's render method should probably
come before the "<a href='/Home'>Home</a>" line in order to have the example's output
come out correctly when viewed in a browser.
This is correct. <body> should come right after the line:

<head><title>Wiki Index</title></head>

IndexPage's render method is missing a closing "</html>" tag in the markup that it
will emit.

siteRoot = rest_wiki.RootResource(wikiData)

Should read:
siteRoot = wiki.RootResource(wikiData)

There's no rest_wiki.py from the previous example -- just wiki.py. The example as
written will result in a NameError exception.

as a first line of this method should be inserted:
xmlrpc.XMLRPC.__init__(self)
If you don't, asking for a dotted function name via XMLRPC
(such as system.listMethods) will result in a Internal Server
error, instead of the expected:
xmlrpclib.Fault: <Fault 8001: 'function get_data not found'>
in addition the server itself outputs an AttributeError, after which
it recovers.

Note from the Author or Editor:
This is correct - the line should be added.

Example 5-5 soap_server.py has an import statement for rest_wiki. However,
there is no such example code - and I think the RootResource being
imported is supposed to be the one in wiki.py.
This is correct, the first line should just read:

import wiki

This method should return a WikiReporter instance, not a RemoteWikiReporter instance

The method name listNeededPages is not allowed to be accessed remotely as it doesn't
conform to the remote_methodName requirement of Perspective Broker. Trying to run
the test client script from example 5-8 results in an error. This line:

def listNeededPages(self):

should instead read:

def remote_listNeededPages(self):

lastname varchar(100),

should read:
lastname varchar(100)

As printed, the example SQL will result in a syntax error and won't work.

FIXME comment still included

Note from the Author or Editor:
The entire comment with the FIXME should be removed.

The news server code connects to Abe's news server (news-server.maine.rr.com) rather
than using sys.argv[1]!

Note from the Author or Editor:
This is correct - it should be 'sys.argv[1]', not 'news-server.maine.rr.com'