Foundations of Python Network Programming 978-1-4302-3004-5

CHAPTER 9 ■ HTTP
• URLs and their structure.
• The GET method and fetching documents.
• How the Host: header makes up for the fact that the hostname from the URL is not
included in the path that follows the word GET.
• The success and error codes returned in HTTP responses and how they induce
browser actions like redirection.
• How persistent connections can increase the speed at which HTTP resources can
be fetched.
• The POST method for performing actions and submitting forms.
• How redirection should always follow the successful POST of a web form.
• That POST is often used for web service requests from programs and can directly
return useful information.
• Other HTTP methods exist and can be used to design web-centric applications
using a methodology called REST.
• Browsers identify themselves through a user agent string, and some servers are
sensitive to this value.
• Requests often specify what content types a client can display, and well-written
servers will try to choose content representations that fit these constraints.
• Clients can request—and servers can use—compression that results in a page
arriving more quickly over the network.
• Several headers and a set of rules govern which HTTP-delivered documents can
and cannot be cached.
• The HEAD command only returns the headers.
• The HTTPS protocol adds TLS/SSL protection to HTTP.
• An old and awkward form of authentication is supported by HTTP itself.
• Most sites today supply their own login form and then use cookies to identify
users as they move across the site.
• If a cookie is captured, it can allow an attacker to view a web site as though the
attacker were the user whose cookie was stolen.
• Even more difficult classes of attack exist on the modern dynamic web, collectively
called cross-site-scripting attacks.
Armed with the knowledge and examples in this chapter, you should be able to use the urllib2
module from the Standard Library to fetch resources from the Web and even implement primitive
browser behaviors like retaining cookies.
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