Embedded HTTP server: Difference between revisions

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{{More citations needed|date=August 2022}}

An '''embedded HTTP server''' is a component of a software system that implements the [[Hypertext Transfer Protocol|HTTP]] protocol. Examples of usage within an application might be:

[[File:2453 IP video server.jpg|thumb|148x200px|right|Front and back views of a small IP video server (Sensoray 2453S) with audio and composite video inputs served via [[HTTP server]] and other protocols.]]

An '''embedded HTTP server''' is an [[HTTP server]] used in an [[embedded system]].

* To provide a [[thin-client]] interface for a traditional application.

* To provide [[indexing]], [[reporting]], and [[debugging]] tools during the development stage.

* To implement a protocol for the distribution and acquisition of information to be displayed in the regular interface — possibly a [[web service]], and possibly using [[XML]] as the data format.

* To develop a [[web application]]

The HTTP server is usually implemented as a [[software component]] of an [[Application software|application]] (embedded) system that controls and/or monitors a machine with mechanical and/or electrical parts.<ref>{{cite journal |title=Edge Computing Using Embedded Webserver with Mobile Device for Diagnosis and Prediction of Metastasis in Histopathological Images |year=2021 |doi=10.1007/s44196-021-00040-x |last1=Johny |first1=Anil |last2=Madhusoodanan |first2=K. N. |journal=International Journal of Computational Intelligence Systems |volume=14 |s2cid=244923748 |doi-access=free }}</ref>

There are a few advantages to using HTTP to perform the above:

* HTTP is a well studied cross-platform protocol and there are mature implementations freely available.

* HTTP is seldom blocked by firewalls and intranet routers.

* HTTP clients (e.g. [[web browser]]s) are readily available with all modern computers.

* There is a growing tendency of using embedded HTTP servers in applications that parallels the rising trends of home-networking and [[ubiquitous computing]].

The HTTP server implements the [[Hypertext Transfer Protocol|HTTP]] [[Communications protocol|protocol]] in order to allow communications with one or more local or remote [[User (computing)|users]] using a [[Web browser|browser]]. The aim is to let users to interact with information provided by the embedded system ([[Web user interface|user interface]], data monitoring, [[Data logger|data logging]], data configuration, etc.) via [[Computer network|network]], without using traditional peripherals required for local user interfaces ([[Display device|display]], [[Computer keyboard|keyboard]], etc.).<ref>{{cite web |title=Administering Security for Oracle HTTP server |url=https://docs.oracle.com/en/middleware/fusion-middleware/web-tier/12.2.1.4/secure-ohs/administering-security-oracle-http-server.pdf}}</ref>

== Typical requirements ==

Natural limitations of the platforms where an embedded HTTP server runs contribute to the list of the functional requirements of the embedded, or more precise, embeddable HTTP server. Some of these requirements in random order

* "Small" RAM and ROM foot print. The exact number depends on the system, but in many cases anything above single digits MB is not embeddable.

* Low CPU consumption.

* Cross compilation support for multiple CPU + OS combinations.

* C implementation (compare with C++/Java/C#).

* Easy integration with existing application, including static link with the OS and application.

* Serving pages from the RAM if there is no file system.

* Modularity.

* Single thread and multi-thread support.

For every specific project requirements can vary significantly. For example, ROM and RAM footprints can be very serious constrain and limit the choices of the system designer. C++ or JVM availability for the CPU/system can be another constrain. Frequently performance is an issue, because typical embedded system runs multiple simultaneous tasks and WEB server is only one of them and usually is a low priority task.

In some cases the functionalities provided via HTTP server allow also program-to-program communications, e.g. to retrieve data logged about the monitored machine, etc.

== Open source servers ==

*[[Jetty (web server)|Jetty]]

*[[Jaminid|Java Mini Daemon]]

*[[Yaws (web server)|Yaws]]

*[[AppWeb_Web_Server|AppWEB]]

*[[KLone (web server)|KLone]]

== Commercial serversUsages ==

Examples of usage within an embedded application might be (e.g.):{{citation needed|date=December 2021}}

*[http://barracudaserver.com/ Barracuda Embedded Web Server SDK]

* Toto provide a [[thin- client]] interface for a traditional application.;

* Toto provide [[indexingDatabase index|index]]ing, [[reportingreport]]ing, and [[debugging]] tools during the development stage.;

* Toto implement a protocol for the distribution and acquisition of information to be displayed in the regular interface — possibly a [[web service]], and possibly using [[XML]] as the [[Serialization|data format.]];

* Toto develop a [[web application]].

== Advantages ==

There are a few advantages to using HTTP to perform the above:{{citation needed|date=December 2021}}

* HTTP is a well studied cross-platform protocol and there are mature implementations freely available.;

* HTTP is seldom blocked by [[Firewall (computing)|firewall]]s and [[intranet]] [[Router (computing)|router]]s;

* HTTP clients (e.g. [[web browser]]s) are readily available with all modern computers.;

* Therethere is a growing tendency of using embedded HTTP servers in applications that parallels the rising trends of [[Home network|home-networking]] and [[ubiquitous computing]].

== Typical requirements ==

Natural limitations of the platforms where an embedded HTTP server runs contribute to the list of the non-functional requirements of the embedded, or more precise, embeddable HTTP server. Some of these requirements inare randomthe following ones.{{citation needed|date=December order2021}}

* "Small" [[Random-access memory|RAM]] and [[Read-only memory|ROM]] foot printfootprint. The exact numbersize depends on the system, but in many cases anything above singleover digitsseveral MBmegabytes is not embeddable.

* Minimal [[CPU]] utilization.

* [[Cross compilation]] support for multiple [[CPU]] +and OS[[operating system]] combinations.

* Easy integration with an existing application, including [[static linklinking]] with the OSoperating system and application.

* Serving [[Web page|page]]s from [[Application software|application]] [[Computer memory|memory]] if there is no [[file system]].

* [[Modular programming|Modularity]].

* Single [[Thread (computing)|thread]] and [[Multithreading (software)|multi-thread]] support.

For every specific project, requirements can vary significantly. For example, ROM and RAM footprints can be a very serious constrainconstraint and limit the choices of the system designer. [[C++]] or [[Java Virtual Machine|JVM]] availability for the CPU/system can be another constrainconstraint. Frequently performance is an issue, because typical embedded systemsystems runsrun multiple simultaneous tasks and WEBan HTTP server is only one of them and usuallymay isbe configured as a low [[Scheduling (computing)|priority]] [[Task (computing)|task]].

== See also ==

* [[Comparison of web serversserver software]]

* [[TinyComparison webof application servers]]

* [[Server (computing)]]

* [[Yaws (webHTTP server)|Yaws]]

* [[Web server]]

==References==

[[Category:Web server software| ]]

{{Reflist}}

== External links ==

{{software-type-stub}}

* [https://www.gnu.org/software/libmicrohttpd/ libmicrohttpd] contains an extensive list of embedded HTTP server libraries towards the bottom of the page

{{network-software-stub}}

* [https://www.keil.com/pack/doc/mw/Network/html/group__net_h_t_t_p___func.html Example: functionalities of an embedded HTTP server component]

[[Category:Web server software| ]]

[[Category:Embedded systems]]