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{{Short description|Data serialization format}}
{{Use dmy dates|date=October 2012}}
'''XML-RPC''' is a remote procedure call (RPC) [[Communications protocol{{Distinguish|protocol]]text which uses [[XML]] to encode its calls and HTTP as a transport mechanism.<ref name="book1">Simon St. Laurent, Joe Johnston, Edd Dumbill. (June 2001) ''Programming Web Services with XML-RPC.'' O'Reilly. First Edition.</ref> "XML-RPC" also refers generically to the use of XML for remote procedure callRPC, independently of the specific protocol. This article is about the protocol named "XML-RPC".}}
{{More citations needed|date=October 2016}}
{{Use dmy dates|date=December 2021}}
'''XML-RPC''' is a [[remote procedure call]] (RPC) [[Communications protocol|protocol]] which uses [[XML]] to encode its calls and [[HTTP]] as a transport mechanism.<ref name="book1">Simon St. Laurent, Joe Johnston, Edd Dumbill. (June 2001) ''Programming Web Services with XML-RPC.'' O'Reilly. First Edition.</ref>
 
==History==
The XML-RPC protocol was created in 1998 by [[Dave Winer]] of [[UserLand Software]] and [[Microsoft]],<ref>{{cite web|last=Box|first=Don|title=A Brief History of SOAP
|publisher=[[O'Reilly Media|O'Reilly]]|date=1 April 2001|url=http://www.xml.com/pub/a/ws/2001/04/04/soap.html
|last=Box
|access-date=27 October 2010}}</ref> with Microsoft seeing the protocol as an essential part of scaling up its efforts in business-to-business e-commerce.<ref>{{Cite web|last=Rupley |first=Sebastian |title=XML's Next Step |work=PC Magazine |access-date=2015-11-17 |date=1999-06-30 |url=http://www.zdnet.com/pcmag/stories/trends/0,7607,2286488,00.html |url-status=dead |archive-url=https://web.archive.org/web/20000304215507/http://www.zdnet.com/pcmag/stories/trends/0,7607,2286488,00.html |archive-date=4 March 2000 }}</ref> As new functionality was introduced, the standard evolved into what is now [[SOAP (protocol)|SOAP]].<ref name=spearheads>{{Cite news|last=Walsh |first=Jeff |title=Microsoft spearheads protocol push |work=Infoworld |access-date=2015-11-17 |date=1999-07-10 |url=http://www.infoworld.com/cgi-bin/displayStory.pl?980710.whsoap.htm |url-status=dead |archive-url=https://web.archive.org/web/19990914001234/http://www.infoworld.com/cgi-bin/displayStory.pl?980710.whsoap.htm |archive-date=14 September 1999 }}</ref>
|first=Don
|title=A Brief History of SOAP
|publisher=[[O'Reilly]]
|date=1 April 2001
|url=http://www.xml.com/pub/a/ws/2001/04/04/soap.html
|accessdate=27 October 2010}}</ref> with Microsoft seeing the protocol as an essential part of scaling up its efforts in business-to-business e-commerce.<ref>{{Cite web|last=Rupley |first=Sebastian |title=XML's Next Step |work=PC Magazine |accessdate=2015-11-17 |date=1999-06-30 |url=http://www.zdnet.com/pcmag/stories/trends/0,7607,2286488,00.html |deadurl=yes |archiveurl=https://web.archive.org/web/20000304215507/http://www.zdnet.com/pcmag/stories/trends/0,7607,2286488,00.html |archivedate=4 March 2000 }}</ref> As new functionality was introduced, the standard evolved into what is now SOAP.<ref name=spearheads>{{Cite news|last=Walsh |first=Jeff |title=Microsoft spearheads protocol push |work=Infoworld |accessdate=2015-11-17 |date=1999-07-10 |url=http://www.infoworld.com/cgi-bin/displayStory.pl?980710.whsoap.htm |deadurl=yes |archiveurl=https://web.archive.org/web/19990914001234/http://www.infoworld.com/cgi-bin/displayStory.pl?980710.whsoap.htm |archivedate=14 September 1999 }}</ref>
 
UserLand supported XML-RPC from version 5.1 of its Frontier web content management system,<ref name=spearheads /> released in June 1998.<ref>{{cite web| last = Walsh| first = Jeff| title = UserLand releases Frontier 5.1, drops freeware model | work = InfoWorld| accessdateaccess-date =November 17, November 2015| date = June 29, June 1998| url = http://www.infoworld.com/cgi-bin/displayStory.pl?980629.wifrontier.htm |archiveurlarchive-url = httphttps://web.archive.org/web/19990915175718/http://www.infoworld.com/cgi-bin/displayStory.pl?980629.wifrontier.htm |archivedate archive-date=15 September 15, 1999 }}</ref>
 
XML-RPC's idea of a human-readable-and-writable, script-parsable standard for HTTP-based requests and responses has also been implemented in competing specifications such as Allaire's [[WDDX|Web Distributed Data Exchange]] (WDDX) and webMethod's [[WIDL (Internet Standard)|Web Interface Definition Language]] (WIDL).<ref>{{Cite news|last=Udell |first=Jon |title=Exploring XML-RPC: DCOM? CORBA? RMI? Why Not Just XML-RPC? |work=Byte |accessdateaccess-date=2015-11-17 |date=1999-06-07 |url=http://www.byte.com/features/1999/06/0607XML_RPC5.html |deadurlurl-status=yesdead |archiveurlarchive-url=https://web.archive.org/web/20000304171225/http://www.byte.com/features/1999/06/0607XML_RPC5.html |archivedatearchive-date=4 March 2000 }}</ref> Prior art wrapping [[Component Object Model|COM]], [[Common Object Request Broker Architecture|CORBA]], and [[Java remote method invocation|Java RMI]] objects in XML syntax and transporting them via HTTP also existed in DataChannel's WebBroker technology.<ref>{{Cite news|volume=20 |issue=21 |last=Walsh |first=Jeff |title=W3C gives a nod to DataChannel's WebBroker |work=Infoworld |accessdateaccess-date=2015-11-17 |date=1998-05-25 |url=http://www.infoworld.com/cgi-bin/displayArchive.pl?/98/21/i06-21.80.htm |deadurlurl-status=yesdead |archiveurlarchive-url=https://web.archive.org/web/19990910213004/http://www.infoworld.com/cgi-bin/displayArchive.pl?/98/21/i06-21.80.htm |archivedatearchive-date=10 September 1999 }}</ref><ref>{{Cite web|last1=Vizard |first1=Michael |last2=Walsh |first2=Jeff |title=DataChannel's Dave Pool talks about shaping the role of XML to suit different needs |work=Infoworld |accessdateaccess-date=2015-12-08 |date=1998-06-29 |url=http://www.infoworld.com/cgi-bin/displayStory.pl?/interviews/980629pool.htm |deadurlurl-status=yesdead |archiveurlarchive-url=https://web.archive.org/web/19990916093829/http://www.infoworld.com/cgi-bin/displayStory.pl?/interviews/980629pool.htm |archivedatearchive-date=16 September 1999 }}</ref>
 
The generic use of XML for [[remote procedure call]] (RPC) was patented by Phillip Merrick, Stewart Allen, and Joseph Lapp in April 2006, claiming benefit to a provisional application filed in March 1998. The patent iswas assigned to [[webMethods]], located in [[Fairfax, VAVirginia]]. The patent expired on March 23, 2019.<ref name= "merrick01">{{cite web |url=http://www.google.com/patents?id=WFV4AAAAEBAJ |archive-url=https://web.archive.org/web/20111203095836/http://www.google.com/patents?id=WFV4AAAAEBAJ |url-status=dead |archive-date=3 December 2011 |title=US Patent 7,028,312 |accessdateaccess-date=18 September 2008 |author=Merrick|date=11 April 2006|display-authors=etal}}</ref>
 
==Usage==
In XML-RPC, worksa client performs an RPC by sending an HTTP request to a server implementingthat theimplements protocol.XML-RPC Theand clientreceives inthe thatHTTP caseresponse. is typically software wanting toA call acan singlehave methodmultiple ofparameters aand remoteone systemresult. Multiple inputThe parametersprotocol candefines bea passedfew todata thetypes remotefor method,the oneparameters returnand value is returnedresult. The parameter types allow nestingSome of parametersthese intodata mapstypes andare listscomplex, thusi.e. largernested. structures can be transported.For Thereforeexample, XML-RPCyou can behave useda toparameter transportthat objectsis oran structuresarray bothof asfive input and as output parametersintegers.
 
The parameters/result structure and the set of data types are meant to mirror those used in common programming languages.
''Identification'' of clients for authorization purposes can be achieved using popular HTTP security methods. Basic access authentication is used for identification, HTTPS is used when identification (via certificates) and encrypted messages are needed. Both methods can be combined.
 
''Identification'' of clients for authorization purposes can be achieved using popular HTTP security methods. [[Basic access authentication]] can be used for identification and authentication.
In comparison to REST, where ''resource representations'' (documents) are transferred, XML-RPC is designed to ''call methods''.
 
In comparison to RESTful protocols, where ''resource representations'' (documents) are transferred, XML-RPC is designed to ''call methods''. The practical difference is just that XML-RPC is much more structured, which means common library code can be used to implement clients and servers and there is less design and documentation work for a specific application protocol. {{Citation needed|reason=This is a vague opinion that doesn't reflect commonly accepted views, XML-RPC adoption having been declining for its lack of reuse and common structure by major actors since the last 20 years|date=August 2024}} One salient technical difference between typical RESTful protocols and XML-RPC is that many RESTful protocols use the HTTP URI for parameter information, whereas with XML-RPC, the URI just identifies the server.
XML-RPC can be argued as simpler than SOAP because it
* allows only one way to serialize methods, whereas SOAP defines multiple different encodings
* has a simpler security model
* does not require (nor support) the creation of WSDL service descriptions, although XRDL provides a simple subset of the functionality provided by WSDL
 
[[JSON-RPC]] is similar to XML-RPC.
 
==Data types==
Common datatypes[[datatype]]s are converted into their XML equivalents with example values shown below:
{| class="wikitable"
!Name
!Tag Example
!Description
|-
|array
|
<syntaxhighlight lang="xml">
<array>
<data>
<value><i4>1404</i4></value>
<value><string>Something here</string></value>
<value><i4>1</i4></value>
</data>
</array>
</syntaxhighlight>
|[[Array data structure|Array]] of values, storing no keys
|-
|base64
|
<syntaxhighlight lang="xml">
<base64>eW91IGNhbid0IHJlYWQgdGhpcyE=</base64>
</syntaxhighlight>
|[[Base64]]-encoded binary data
|-
|boolean
|
<syntaxhighlight lang="xml">
<boolean>1</boolean>
</syntaxhighlight>
|[[Boolean data type|Boolean]] logical value (0 or 1)
|-
|date/time
|
<syntaxhighlight lang="xml">
<dateTime.iso8601>19980717T14:08:55Z</dateTime.iso8601>
</syntaxhighlight>
|Date and time in [[ISO 8601]] format
|-
|double
|
<syntaxhighlight lang="xml">
<double>-12.53</double>
</syntaxhighlight>
|[[Double precision]] floating point number
|-
|integer
|
<syntaxhighlight lang="xml">
<int>42</int>
</syntaxhighlight>
or
<syntaxhighlight lang="xml">
<i4>42</i4>
</syntaxhighlight>
|Signed [[integer]] coded on 4 bytes
|-
|string
|
<syntaxhighlight lang="xml">
<string>Hello world!</string>
</syntaxhighlight>
or
<syntaxhighlight lang="xml">
Hello world!
</syntaxhighlight>
|String of characters. Must follow [[XML#Characters and escaping|XML encoding]].
|-
|struct
|
<syntaxhighlight lang="xml">
<struct>
<member>
<name>foo</name>
<value><i4>1</i4></value>
</member>
<member>
<name>bar</name>
<value><i4>2</i4></value>
</member>
</struct>
</syntaxhighlight>
|[[Associative array]]
|-
|nil
|
<syntaxhighlight lang="xml">
<nil/>
</syntaxhighlight>
|[[nullable type|Discriminated null value]]; an XML-RPC [https://web.archive.org/web/20050911054235/http://ontosys.com/xml-rpc/extensions.php extension]
|
|-
|long
|
<syntaxhighlight lang="xml">
<i8>1312</i8>
</syntaxhighlight>
|Signed integer coded on 8 bytes. This is not part of the specification, but it is supported by several XML-RPC implementations<ref>{{cite web |title=RPC::XML - A set of classes for core data, message and XML handling - metacpan.org |work=MetaCPAN |url=https://metacpan.org/pod/RPC::XML |access-date=13 April 2025}}</ref>{{,}}<ref>{{cite web |title=User manual for XML-RPC For C/C++ |url=https://xmlrpc-c.sourceforge.io/doc/libgeneral.html |access-date=13 April 2025}}</ref>
|}
 
==Examples==
An example of a typical XML-RPC request would be:
<sourcesyntaxhighlight lang="xml">
<?xml version="1.0"?>
<methodCall>
Line 47 ⟶ 141:
</params>
</methodCall>
</syntaxhighlight>
</source>
 
An example of a typical XML-RPC response would be:
<sourcesyntaxhighlight lang="xml">
<?xml version="1.0"?>
<methodResponse>
Line 59 ⟶ 153:
</params>
</methodResponse>
</syntaxhighlight>
</source>
 
A typical XML-RPC fault would be:
<sourcesyntaxhighlight lang="xml">
<?xml version="1.0"?>
<methodResponse>
Line 80 ⟶ 174:
</fault>
</methodResponse>
</syntaxhighlight>
</source>
 
== Criticism ==
Recent critics (from 2010 and onwards) of XML-RPC argue that RPC calls can be made with plain XML, and that XML-RPC does not add any value over XML. Both XML-RPC and XML require an application-level data model, such as which field names are defined in the XML schema or the parameter names in XML-RPC. Furthermore, XML-RPC uses about 4 times the number of bytes compared to plain XML to encode the same objects, which is itself verbose compared to [[JSON]].<ref>
{{cite web
| url = httphttps://stackoverflow.com/questions/1376688
| title = What is the benefit of XML-RPC over plain XML?
| date = 9 September 2009
| publisher = [[Stack Overflow]]
| accessdateaccess-date = 7 April 2011
}}
</ref><ref>
Line 96 ⟶ 190:
| title = An open poll on the merits of XmlRpc versus alternatives
| date = 22 November 2006
| publisher = [http://www.intertwingly.net intertwingly.net]
| accessdateaccess-date = 7 April 2011
}}
</ref><ref>
{{cite web
| url = http://joncanady.com/blog/2010/01/14/if-you-have-rest-why-xml-rpc/
| title = If you have REST, why XML-RPC?
| author = Jon Canady
| date = 14 January 2010
| publisher = [http://joncanady.com joncanady.com]
| accessdateaccess-date = 7 April 2011
|url-status = dead
|archive-url = https://web.archive.org/web/20130511053512/http://joncanady.com/blog/2010/01/14/if-you-have-rest-why-xml-rpc/
|archive-date = 11 May 2013
}}
</ref>
 
==See Implementations also==
 
* [[Weblogs.com]]
=== Ruby ===
* [[Pingback]]
* XML-RPC Client in stdlib
*[[Ajax (programming)]]
* XML-RPC Server in stdlib
*[[Software componentry#Technologies for Software Components|Component technologies]]
 
*[[Comparison of data serialization formats]]
=== Python ===
*[[OPML]]
* xmlrpclib
*[[JSON-RPC]]
** Renamed [https://docs.python.org/3.1/library/xmlrpc.client.html xmlrpc.client] in Python 3.
*[[Web service]]
* Creating XML-RPC Servers and Clients with Twisted
*[[gRPC]]
 
=== C++ ===
* Libiqxmlrpc
* Ultra lightweight XML-RPC library for C++
* XML-RPC for C and C++
* XmlRpc++
* XmlRpc C++ client for Windows
* gSOAP toolkit for C and C++ supporting XML-RPC and more
* libmaia: XML-RPC for Qt/C++
* XML-RPC Client S60: XML-RPC for Symbian/C++
* Cxxtools XML-RPC C++ Client and Server for POSIX. It's part of Tntnet project.
* AnyRPC Supports multiple RPC protocols including XML-RPC
 
=== Objective-C / GNUstep / Cocoa ===
* XMLRPC Framework
 
=== Erlang ===
* XML-RPC for Erlang: This is an HTTP 1.1 compliant XML-RPC library for Erlang. It is designed to make it easy to write XML-RPC Erlang clients and/or servers. The library is compliant with the XML-RPC specification published by <nowiki>http://www.xmlrpc.org/</nowiki>
 
=== Groovy ===
* XML-RPC Module
 
=== Java ===
* Apache XML-RPC: Open source library for Java
* XML-RPC Delight: Convenient serialisation/deserialisation for Apache XML-RPC using Java Annotations and Beans
* [http://members.fortunecity.com/neptune42/xmlrpc/index.htm]: Secure Apache XML-RPC
* Redstone XML-RPC Library: Redstone's Open Source Library – XML-RPC implementation in Java
* XML-RPC Library for Java ME: Open source client-side library for Java ME
* aXMLRPC: Open source XML-RPC client library for Java and Android
* Nmote-xr: Open source BSD style client/server library with minimal dependencies
 
=== JavaScript ===
* XML-RPC for Node.js: Open source JavaScript XML-RPC client and server for node.js
* Mimic XML-RPC: Open source JavaScript XML-RPC client cross-browser.
* XML-RPC for Javascript: Open source library implementing the XML-RPC and JSON-RPC protocols, written in Javascript.
* XML-RPC for Google Polymer: A Google polymer component that deals with XML-RPC resources.
 
=== XMPP ===
* pyJabberXMLRPC: Python classes for XMPP
* Jabber-RPC: Over the Extensible Messaging and Presence Protocol protocol
 
=== PHP ===
* XmlRpc in Zend_Framework 1.12: XmlRpc Server and Client in Zend_Framework 1.12
* XmlRpc in Zend_Framework 2.2: XmlRpc Server and Client in Zend_Framework 2
* XML-RPC for PHP: a library implementing the XML-RPC protocol, written in PHP
 
=== Perl ===
* RPC::XML: A set of Perl classes for core data, message and XML handling
* Frontier::RPC: Another set of Perl modules for XML-RPC client/server implementation
* XML::Compile::RPC: RPC extension to XML::Compile
 
=== Other ===
* JSON/XML-RPC Client and Server: Abstract away the differences between JSON-RPC and XML-RPC
* RemObjects SDK Delphi and .NET package for XML-RPC, in addition to SOAP and others
* RealThinClient SDK: For Delphi/C++
* XML-RPC for ActionScript: For Flash ActionScript 2.0
* as3-rpclib: For Flex/Actionscript 3
* XML-RPC.NET: Open source library for .NET clients and servers
* XmlRpc-Light: Client and server library for OCaml
* S-XML-RPC: Client and server library for Common Lisp
* clj-xmlrpc: XML-RPC client for Clojure
* necessary-evil: XML-RPC Client and Ring-based Server for Clojure
* HaXR: Client and server library for Haskell
* Ruby XML-RPC library: For Ruby
* XML-RPC interface to Lua: For Lua
* android-xmlrpc: A light XML-RPC client for Google Android
* XML-RPC for Tcl: A Tcl implementation of XML-RPC providing client and server support
* RebXR: a full client/server XML-RPC implementation for REBOL
 
==See also==
*Ajax (programming)
*Component technologies
*Comparison of data serialization formats
*OPML
*Web service
 
==References==
Line 200 ⟶ 223:
 
==External links==
* {{web archive|url=https://web.archive.org/web/20130113041824/http://xmlrpc.scripting.com/default.html|title=Official website}}
* XML-RPC Homepage
* Forum
* Tutorials
* Technology Reports
* Citations from CiteSeer
* Relax-NG schema for XML-RPC
 
{{DEFAULTSORT:Xml-Rpc}}
Retrieved from "https://en.wikipedia.org/wiki/XML-RPC"