book

Twisted Network Programming Essentials, 2nd Edition

by Abe Fettig, Jessica McKellar

March 2013

Beginner

191 pages

4h 9m

English

O'Reilly Media, Inc.

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Why Use Twisted?What This Book CoversConventions Used in This BookWhat You’ll NeedChanges Since the Previous EditionUsing Code ExamplesSafari® Books OnlineHow to Contact UsAcknowledgments
Installing TwistedInstallation on LinuxMore package options and optional dependenciesInstallation on WindowsOptional dependenciesAdding Twisted utilities to your PATHInstallation on OS XOptional dependenciesInstalling from SourceRequired DependenciesInstalling a C compilerInstalling zope.interfaceInstalling Twisted from a Release TarballInstalling Twisted from a Source CheckoutInstalling Optional Dependencies from SourceTesting Your InstallationUsing the Twisted DocumentationAPI DocumentationSubproject DocumentationFinding Answers to Your QuestionsMailing ListsIRC ChannelsStack OverflowTwisted Blogs
A TCP Echo Server and ClientEvent-Driven ProgrammingThe ReactorTransportsProtocolsProtocol FactoriesDecoupling Transports and ProtocolsA TCP Quote Server and ClientProtocol State MachinesMore Practice and Next Steps
What Deferreds Do and Don’t DoThe Structure of a Deferred ObjectCallback Chains and Using Deferreds in the ReactorPractice: What Do These Deferred Chains Do?Exercise 1Exercise 2Exercise 3Exercise 4Exercise 5Exercise 6The Truth About addCallbacksExercise 7Exercise 8Key Facts About DeferredsSummary of the Deferred APIMore Practice and Next Steps
Responding to HTTP Requests: A Low-Level ReviewThe Structure of an HTTP RequestParsing HTTP RequestsHandling GET RequestsServing Static ContentStatic URL dispatchServing Dynamic ContentDynamic DispatchCreating resources that are both renderable and have childrenRedirectsHandling POST RequestsA Minimal POST ExampleAsynchronous ResponsesMore Practice and Next Steps
Basic HTTP Resource RetrievalPrinting a Web ResourceDownloading a Web ResourceAgentRequesting Resources with AgentRetrieving Response MetadataPOSTing Data with AgentMore Practice and Next Steps
The Twisted Application InfrastructureServicesApplicationsTAC FilestwistdPluginsMore twistd ExamplesMore Practice and Next StepsSuggested Exercises

Basic In-Application Loggingtwistd LoggingCustom LoggersKey Facts and Caveats About Logging
Nonblocking Database QueriesMore Practice and Next Steps
The Components of Twisted CredTwisted Cred: An ExampleCredentials CheckersAuthentication in Twisted ApplicationsMore Practice and Next Steps
ThreadsSubprocessesRunning a Subprocess and Getting the ResultCustom Process ProtocolsMore Practice and Next Steps
Writing and Running Twisted Unit Tests with TrialTesting ProtocolsTests and the ReactorTesting DeferredsTesting the Passage of TimeMore Practice and Next Steps
IRC ClientsIRC ServersMore Practice and Next Steps
SMTP Clients and ServersThe SMTP ProtocolSending Emails Using SMTPSMTP ServersStoring MailIMAP Clients and ServersIMAP ServersIMAP ClientsPOP3 Clients and ServersPOP3 ServersMore Practice and Next Steps
SSH ServersA Basic SSH ServerUsing Public Keys for AuthenticationProviding an Administrative Python ShellRunning Commands on a Remote ServerSSH ClientsMore Practice and Next Steps
Contributing to Twisted

Content preview from Twisted Network Programming Essentials, 2nd Edition

Chapter 14. SSH

SSH, the Secure SHell, is an essential tool for many developers and administrators. SSH provides a way to establish encrypted, authenticated connections. The most common use of an SSH connection is to get a remote shell, but it’s possible to do many other things through SSH as well, including transferring files and tunneling other connections.

The twisted.conch package adds SSH support to Twisted. This chapter shows how you can use the modules in twisted.conch to build SSH servers and clients.

SSH Servers

The command line is an incredibly efficient interface for certain tasks. System administrators love the ability to manage applications by typing commands without having to click through a graphical user interface. An SSH shell is even better, as it’s accessible from anywhere on the Internet.

You can use twisted.conch to create an SSH server that provides access to a custom shell with commands you define. This shell will even support some extra features, like command history, so that you can scroll through the commands you’ve already typed.

A Basic SSH Server

To write an SSH server, implement a subclass of twisted.conch.recvline.HistoricRecvLine that implements your shell protocol. HistoricRecvLine is similar to twisted.protocols.basic.LineReceiver, but with higher-level features for controlling the terminal.

To make your shell available through SSH, you need to implement a few different classes that twisted.conch needs to build an SSH server. First, you need ...