An embedded HTTP server is an

HTTP server An HTTP server is a computer (software) program (or even a software component included in an other program) that plays the role of a server in a client–server model by implementing the ''server part'' of the HTTP and/or HTTPS network proto ...

used in an

embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...

. The HTTP server is usually implemented as a

software component Component-based software engineering (CBSE), also called component-based development (CBD), is a branch of software engineering that emphasizes the separation of concerns with respect to the wide-ranging functionality available throughout a give ...

of an application (embedded) system that controls and/or monitors a machine with mechanical and/or electrical parts. The HTTP server implements the

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

protocol Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

in order to allow communications with one or more local or remote

users Ancient Egyptian roles * User (ancient Egyptian official), an ancient Egyptian nomarch (governor) of the Eighth Dynasty * Useramen, an ancient Egyptian vizier also called "User" Other uses * User (computing), a person (or software) using a ...

using a browser. The aim is to let users to interact with information provided by the embedded system (

user interface In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine f ...

, data monitoring,

data logging A data logger (also datalogger or data recorder) is an electronic device that records data over time or about location either with a built-in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they a ...

, data configuration, etc.) via

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

, without using traditional peripherals required for local user interfaces (

display Display may refer to: Technology * Display device, output device for presenting information, including: ** Cathode ray tube, video display that provides a quality picture, but can be very heavy and deep ** Electronic visual display, output dev ...

, keyboard, etc.). 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.

Usages

Examples of usage within an embedded application might be (e.g.): * to provide a

thin client In computer networking, a thin client is a simple (low-performance) computer that has been optimized for establishing a remote connection with a server-based computing environment. They are sometimes known as ''network computers'', or in ...

interface for a traditional application; * to provide

index Index (or its plural form indices) may refer to: Arts, entertainment, and media Fictional entities * Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index'' * The Index, an item on a Halo megastru ...

ing,

report A report is a document that presents information in an organized format for a specific audience and purpose. Although summaries of reports may be delivered orally, complete reports are almost always in the form of written documents. Usage In ...

ing, and

debugging In computer programming and software development, debugging is the process of finding and resolving ''bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems. Debugging tactics can involve in ...

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 Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. ...

as the data format; * to develop a

web application A web application (or web app) is application software that is accessed using a web browser. Web applications are delivered on the World Wide Web to users with an active network connection. History In earlier computing models like client-serve ...

Advantages

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

firewall Firewall may refer to: * Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts * Firewall (construction), a barrier inside a building, designed to limit the spre ...

s and intranet routers; * HTTP clients (e.g.

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on ...

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 Ubiquitous computing (or "ubicomp") is a concept in software engineering, hardware engineering and computer science where computing is made to appear anytime and everywhere. In contrast to desktop computing, ubiquitous computing can occur using ...

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 are the following ones. * "Small"

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch ...

and

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

footprint. The exact size depends on the system, but in many cases anything over several megabytes is not embeddable. * Minimal

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

utilization. *

Cross compilation A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running. For example, a compiler that runs on a PC but generates code that runs on an Android smartphone is a cross c ...

support for multiple

and

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

combinations. * Easy integration with an existing application, including

static linking In computer science, a static library or statically-linked library is a set of routines, external functions and variables which are resolved in a caller at compile-time and copied into a target application by a compiler, linker, or binder, produc ...

with the operating system and application. * Serving

page Page most commonly refers to: * Page (paper), one side of a leaf of paper, as in a book Page, PAGE, pages, or paging may also refer to: Roles * Page (assistance occupation), a professional occupation * Page (servant), traditionally a young ma ...

s from application

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

if there is no

file system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one lar ...

. *

Modularity Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a s ...

. * Single

thread Thread may refer to: Objects * Thread (yarn), a kind of thin yarn used for sewing ** Thread (unit of measurement), a cotton yarn measure * Screw thread, a helical ridge on a cylindrical fastener Arts and entertainment * ''Thread'' (film), 2016 ...

and multi-thread support. For every specific project, requirements can vary significantly. For example, ROM and RAM footprints can be a very serious constraint and limit the choices of the system designer. C++ or

JVM A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describes ...

availability for the system can be another constraint. Frequently performance is an issue, because typical embedded systems run multiple simultaneous tasks and an HTTP server is only one of them and may be configured as a low priority task.

References

{{Reflist

External links

libmicrohttpd
contains an extensive list of embedded HTTP server libraries towards the bottom of the page

* ttps://realtimelogic.com/articles/What-is-an-Embedded-Application-Server Embedded Web Server vs. Embedded Application Server

Usages

Advantages

Typical requirements

See also

References

External links