Twisted (software)

Last updated
Twisted
Original author(s) Glyph Lefkowitz
Developer(s) Community
Initial releaseOctober 22, 2002;22 years ago (2002-10-22) [1]
Stable release
24.7.0 [2]   OOjs UI icon edit-ltr-progressive.svg / 10 August 2024;2 months ago (10 August 2024)
Repository
Written in Python
Type Event-driven networking
License MIT License
Website www.twistedmatrix.com   OOjs UI icon edit-ltr-progressive.svg

Twisted is an event-driven network programming framework written in Python and licensed under the MIT License.

Contents

Twisted projects variously support TCP, UDP, SSL/TLS, IP multicast, Unix domain sockets, many protocols (including HTTP, XMPP, NNTP, IMAP, SSH, IRC, FTP, and others), and much more. Twisted is based on the event-driven programming paradigm, which means that users of Twisted write short callbacks which are called by the framework.

Core ideas

Separation of protocols and transports

Twisted is designed for complete separation between logical protocols (usually relying on stream-based connection semantics, such as HTTP or POP3) and physical transport layers supporting such stream-based semantics (such as files, sockets or SSL libraries). Connection between a logical protocol and a transport layer happens at the last possible moment — just before information is passed into the logical protocol instance. The logical protocol is informed of the transport layer instance, and can use it to send messages back and to check for the peer's identity. Note that it is still possible, in protocol code, to deeply query the transport layer on transport issues (such as checking a client-side SSL certificate). Naturally, such protocol code will fail (raise an exception) if the transport layer does not support such semantics.

Deferreds

Central to the Twisted application model is the concept of a deferred (elsewhere called a future ). A deferred is an instance of a class designed to receive and process a result which has not been computed yet, for example because it is based on data from a remote peer. Deferreds can be passed around, just like regular objects, but cannot be asked for their value. Each deferred supports a callback chain. When the deferred gets the value, it is passed to the functions on the callback chain, with the result of each callback becoming the input for the next. Deferreds make it possible to operate on the result of a function call before its value has become available.

For example, if a deferred returns a string from a remote peer containing an IP address in quad format, a callback can be attached to translate it into a 32-bit number. Any user of the deferred can now treat it as a deferred returning a 32-bit number. This, and the related ability to define "errbacks" (callbacks which are called as error handlers), allows code to specify in advance what to do when an asynchronous event occurs, without stopping to wait for the event. In non-event-driven systems, for example using threads, the operating system incurs premature and additional overhead organizing threads each time a blocking call is made.

Thread support

Twisted supports an abstraction over raw threads — using a thread as a deferred source. Thus, a deferred is returned immediately, which will receive a value when the thread finishes. Callbacks can be attached which will run in the main thread, thus alleviating the need for complex locking solutions. A prime example of such usage, which comes from Twisted's support libraries, is using this model to call into databases. The database call itself happens on a foreign thread, but the analysis of the result happens in the main thread.

Foreign loop support

Twisted can integrate with foreign event loops, such as those of GTK+, Qt and Cocoa (through PyObjC). This allows using Twisted as the network layer in graphical user interface (GUI) programs, using all of its libraries without adding a thread-per-socket overhead, as using Python's native library would. A full-fledged web server can be integrated in-process with a GUI program using this model, for example.

Applications using Twisted

Nevow

Original author(s) Donovan Preston [15] [16] [17]
Developer(s) Divmod
Initial releaseMay 6, 2004;20 years ago (2004-05-06)
Stable release
0.14.4 / June 14, 2018;6 years ago (2018-06-14) [18]
Repository
Written in Python
Operating system Cross-platform
Type Web application framework
License MIT License
Website www.twistedmatrix.com   OOjs UI icon edit-ltr-progressive.svg

Nevow (pronounced like the French nouveau) is a Python web application framework originally developed by the company Divmod. Template substitution is achieved via a small Tag Attribute Language, which is usually embedded in on-disk XML templates, though there is also a pure-Python domain-specific language called Stan, for expressing this markup programmatically. Nevow integrates well with Twisted.

Nevow was deployed on several high-profile web sites, most notably the official Python site. [19]

As of mid-2010, Divmod went out of business, [20] causing development work on Nevow to all but cease, and in 2011 its homepage was no longer accessible. [21] There is a project on Launchpad, hosting the source code of Divmod [22] including the source code of the Nevow project. [23]

Athena

Athena is a Nevow component which facilitates bi-directional, asynchronous communication between the Python and JavaScript portions of a web application in the form of remote procedure calls. This technique is typically called Ajax or Comet, though Nevow's implementation predates both of these labels. [24] Athena also includes an inheritance-based JavaScript object system, which forms the basis of a client-side widget abstraction, module system and in-browser unit testing kit.

See also

Related Research Articles

The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between systems on different operating systems, programming languages, and computing hardware. CORBA uses an object-oriented model although the systems that use the CORBA do not have to be object-oriented. CORBA is an example of the distributed object paradigm.

Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network, such as the Internet. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securing HTTPS remains the most publicly visible.

lighttpd

lighttpd is an open-source web server optimized for speed-critical environments while remaining standards-compliant, secure and flexible. It was originally written by Jan Kneschke as a proof-of-concept of the c10k problem – how to handle 10,000 connections in parallel on one server, but has gained worldwide popularity. Its name is a portmanteau of "light" and "httpd".

Datagram Transport Layer Security (DTLS) is a communications protocol providing security to datagram-based applications by allowing them to communicate in a way designed to prevent eavesdropping, tampering, or message forgery. The DTLS protocol is based on the stream-oriented Transport Layer Security (TLS) protocol and is intended to provide similar security guarantees. The DTLS protocol datagram preserves the semantics of the underlying transport—the application does not suffer from the delays associated with stream protocols, but because it uses User Datagram Protocol (UDP) or Stream Control Transmission Protocol (SCTP), the application has to deal with packet reordering, loss of datagram and data larger than the size of a datagram network packet. Because DTLS uses UDP or SCTP rather than TCP it avoids the TCP meltdown problem when being used to create a VPN tunnel.

The Perl Object Environment (POE) is a library of Perl modules written in the Perl programming language by Rocco Caputo et al.

SAP NetWeaver Application Server or SAP Web Application Server is a component of SAP NetWeaver which works as a web application server for SAP products. All ABAP application servers including the message server represent the application layer of the multitier architecture of an ABAP-based SAP system. These application servers execute ABAP applications and communicate with the presentation components, the database, and also with each other, using the message server.

Comet is a web application model in which a long-held HTTPS request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term, encompassing multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins. The Comet approach differs from the original model of the web, in which a browser requests a complete web page at a time.

<span class="mw-page-title-main">Network Security Services</span> Collection of cryptographic computer libraries

Network Security Services (NSS) is a collection of cryptographic computer libraries designed to support cross-platform development of security-enabled client and server applications with optional support for hardware TLS/SSL acceleration on the server side and hardware smart cards on the client side. NSS provides a complete open-source implementation of cryptographic libraries supporting Transport Layer Security (TLS) / Secure Sockets Layer (SSL) and S/MIME. NSS releases prior to version 3.14 are tri-licensed under the Mozilla Public License 1.1, the GNU General Public License, and the GNU Lesser General Public License. Since release 3.14, NSS releases are licensed under GPL-compatible Mozilla Public License 2.0.

The Spring Framework is an application framework and inversion of control container for the Java platform. The framework's core features can be used by any Java application, but there are extensions for building web applications on top of the Java EE platform. The framework does not impose any specific programming model.. The framework has become popular in the Java community as an addition to the Enterprise JavaBeans (EJB) model. The Spring Framework is free and open source software.

Lightstreamer is a web-based asynchronous messaging project, implementing the WebSocket protocol, the Comet model, the push technology paradigm, and the real-time web practices.


This is a comparison of notable free and open-source configuration management software, suitable for tasks like server configuration, orchestration and infrastructure as code typically performed by a system administrator.

Thrift is an IDL and binary communication protocol used for defining and creating services for programming languages. It was developed by Facebook. Since 2020, it is an open source project in the Apache Software Foundation.

The reactor software design pattern is an event handling strategy that can respond to many potential service requests concurrently. The pattern's key component is an event loop, running in a single thread or process, which demultiplexes incoming requests and dispatches them to the correct request handler.

Web2py is an open-source web application framework written in the Python programming language. Web2py allows web developers to program dynamic web content using Python. Web2py is designed to help reduce tedious web development tasks, such as developing web forms from scratch, although a web developer may build a form from scratch if required.

Netty is a non-blocking I/O client-server framework for the development of Java network applications such as protocol servers and clients. The asynchronous event-driven network application framework and tools are used to simplify network programming such as TCP and UDP socket servers. Netty includes an implementation of the reactor pattern of programming. Originally developed by JBoss, Netty is now developed and maintained by the Netty Project Community.

<span class="mw-page-title-main">SoftEther VPN</span> Open-source VPN client and server software

SoftEther VPN is free open-source, cross-platform, multi-protocol VPN client and VPN server software, developed as part of Daiyuu Nobori's master's thesis research at the University of Tsukuba. VPN protocols such as SSL VPN, L2TP/IPsec, OpenVPN, and Microsoft Secure Socket Tunneling Protocol are provided in a single VPN server. It was released using the GPLv2 license on January 4, 2014. The license was switched to Apache License 2.0 on January 21, 2019.

WAMP is a WebSocket subprotocol registered at IANA, specified to offer routed RPC and PubSub. Its design goal is to provide an open standard for soft, real-time message exchange between application components and ease the creation of loosely coupled architectures based on microservices. Because of this, it is a suitable enterprise service bus (ESB), fit for developing responsive web applications or coordinating multiple connected IoT devices.

The Asynchronous Server Gateway Interface (ASGI) is a calling convention for web servers to forward requests to asynchronous-capable Python frameworks, and applications. It is built as a successor to the Web Server Gateway Interface (WSGI).

References

  1. ↑ Shtull-Trauring, Itamar (2002-10-22). "Twisted 1.0". twisted-python (Mailing list). Retrieved 2008-08-14.
  2. ↑ "Release 24.7.0". 10 August 2024. Retrieved 27 August 2024.
  3. ↑ "BuildBot Manual". github.com. Archived from the original on 2012-07-29. Retrieved 2017-10-28.
  4. ↑ "Python Slithers into Systems". eweek.com.
  5. ↑ SageMath#Features
  6. ↑ Sage a Basic Overview [ permanent dead link ]
  7. ↑ "mistah deejay". omegler.blogspot.com.
  8. ↑ "Google Groups". groups.google.com.
  9. ↑ "Calendar and Contacts Server". www.calendarserver.org.
  10. ↑ "Twitch - Jobs". Twitch.
  11. ↑ "Velocity Weather -". www.velocityweather.com.
  12. ↑ A WebSocket-oriented monitor for Wikipedia (also, wikimon, wikital monsters), hatnote, 2017-09-03, retrieved 2017-09-21
  13. ↑ "Deluge: build from source". dev.deluge-torrent.org. Retrieved 2020-01-08.
  14. ↑ "Magic Wormhole". github.com.
  15. ↑ this 2004 paper by Donovan Preston, the original author of Nevow and Formless Archive index at the Wayback Machine
  16. ↑ Nevow: A Web Application Construction Kit, Donovan Preston
  17. ↑ Subject: Re: ANN: Twisted 1.1.0, the framework of *your* internet, From: Donovan Preston, Date: 2003-10-27, Newsgroups: gmane.comp.python.twisted, nevow was originally a research project -- a weekend's worth of hacking whose benefits turned out to be so great that we decided to focus on bringing it up to a usable state for Quotient as soon as possible. And that's where it is now.
  18. ↑ "Releases · twisted/nevow". GitHub . Retrieved 2020-11-04.
  19. ↑ PythonWebsitePyramidDocs, Pyramid is the internal website templating system used to build the python.org pages. (It is not connected to the Pyramid web framework, formerly named BFG, that's used with Pylons.) Pyramid uses Nevow as its templating system and YAML as the format for its file based data - PythonInfo Wiki, python.org
  20. ↑ Goodbye, Divmod. Hello, World!, July 10, 2009, Deciphering Glyph
  21. ↑ Divmod Nevow commits Archived 2012-10-15 at the Wayback Machine on Ohloh
  22. ↑ Divmod Archived August 13, 2006, at the Wayback Machine
  23. ↑ Divmod on Launchpad
  24. ↑ History Archived 2016-03-03 at the Wayback Machine , Nevow Athena from Scratch, or The Evolution of a Chat Application — Divmod Nevow vtrunk documentation
  25. ↑ "EventMachine" . Retrieved 20 August 2011.
  26. ↑ "Integrating with other Frameworks — Kivy 1.11.0.dev0 documentation". kivy.org.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.