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emWeb—Web Server

  • Provide easy to use graphical interfaces for control or data acquisition
  • Compatible with all browsers for PC/Mac and mobile devices
  • Supports modern standards like WebSockets (additional add-on), REST, SSE and many more
  • Independent of the TCP/IP stack: any stack with sockets can be used
  • Can be used on embedded targets or PC (Windows/Linux/...) and Mac
  • Samples for embedded targets and PC included, showing simple and advanced use cases
  • High performance
  • Small footprint
  • Smallest configuration can run in a single task for multiple connections

emWeb—Web Server

Provide easy to use graphical interfaces to control your target.
Can be used from any device that has a browser such as PC/Mac and mobile devices.
Easy to maintain by separating design and content.

Provide easy to use graphical user interfaces that can be accessed from anywhere!

emWeb allows you to use the most widely accepted language for providing Graphical User Interfaces in the world, HTML.

emWeb allows you to provide an operating system independent user interface (UI). The UI can be designed in a range from very basic/simple up to full replacements for traditional application GUIs, using technologies like JavaScript, AJAX, SSE, WebSockets and more. This way the target can be operated from any device that features a browser.

emWeb can not only be incorporated into embedded targets, but PC/Mac or even mobile applications as well.

Even targets that do not feature traditional network access via Ethernet cable or WiFi access can benefit by using a browser UI. With the IP-over-USB technology, SEGGER provides a state-of-the-art solution for USB devices to be powered by a browser UI.

Design only one UI that will work on any end user device.

Advantages

For your product, using a browser based UI comes with a lot of advantages over a traditional application GUI. The biggest advantage, of course, is that you can operate the target from any host that features a browser, independent of the operating system. While this is a clear advantage to the programmer and designer of an UI, there are even more advantages for your customers, making your device more user friendly than ever before:

  • No software to download or install
  • Can be accessed and configured using any device with a browser (PC/Mac or mobile devices like smartphones or tablets)
  • Can even be made available over the Internet


Devices using browser UIs

Devices using browser UIs are becoming more and more the state-of-the-art standard. The following is a list of devices already using browser UIs for configuration purposes today:

  • Routers, switches and Access Points
  • Almost any IoT device
  • Printers
  • Debug probes
  • Oscilloscopes
  • All kinds of gadgets

Let's look at the following examples:

Printers

Printers are a popular examples for devices that already use a browser UI for configuration, at least if they support a network interface like Ethernet or WiFi anyhow.

While a browser based UI is typically thought of being exclusive to Ethernet or WiFi capable devices, this is not where it has to end!

Even targets that do not feature traditional network access via Ethernet cable or WiFi access can benefit by using a browser UI. With the IP-over-USB technology, SEGGER provides a state-of-the-art solution for USB devices to be powered by a browser UI. This allows using the same UI for device families that come in different models and features regarding their host interfaces.

An example for this would be different printer models of the same product family that come with different host interfaces. One model might come with USB only while another model features USB, Ethernet cable and WiFi. All of them can share the same browser UI.

printer_simple_390.png

Gadgets

Using the IP-over-USB technology, basically all devices that come with an USB connector can feature a browser UI. As almost all modern devices use regular USB for charging, this means all of these products are ready by their hardware to feature this state-of-the-art technology.

Typical examples of devices that benefit from a browser UI are non-stationary like:

  • Wireless headphones (configuration of presets)
  • MP3 player (configuration and playlist management)
  • Fitness tracker (configuration and statistics)


emUSB-IP headphone

Other examples

Using a browser based UI is not exclusive to an external device being accessed. Due to the fact that a browser UI is operating system independent, it makes a great alternative for any kind of application GUI. UIs designed this way can also be easily integrated into other application. An example would be a configuration page of one application/product that can easily be added into any other application using the WebKit engine.

 

 

Requirements

TCP/IP stack

emWeb requires a TCP/IP stack. It is optimized for embOS/IP, but any RFC-compliant TCP/IP stack can be used. The shipment includes a Win32 implementation sample which uses the standard Winsock API, as well as an implementation which uses the socket API of embOS/IP.

Multi Tasking

The web server needs to run as a separate thread. Therefore, a multi tasking system is required to use the web server emWeb.

 

 

Resource usage

HTTP backgrounds

HTTP is a communication protocol originally designed to transfer information via hypertext pages. The development of HTTP is coordinated by the IETF (Internet Engineering Task Force) and the W3C (World Wide Web Consortium). The typically used protocol version is still 1.1 that gets extended by various sub-protocols.

The HTTP protocol itself is implemented on top of the TCP protocol.

HTTP Communication Basics

HTTP is a challenge and response protocol. A client initiates a TCP connection to the Web server and sends a HTTP request. A HTTP request starts with a method token. [RFC 2616] defines 8 method tokens. The method token indicates the method to be performed on the requested resource. emWeb implements the major methods which are typically required.

HTTP method Description
GETThe GET method means that it retrieves whatever information is identified by the Request-URI.
POSTThe POST method submits data to be processed to the identified resource. The data is included in the body of the request.

Dynamic content

emWeb supports different techniques to create dynamic pages.

TechniqueDescription
CGIs

The Common Gateway Interface (CGI) is a replace mechanism that is used in conjunction with a template page. A visitor counter in a page with static content would be one of the simplest use cases.

The template page can be a simple HTML page with a placeholder for the counter value. Whenever the page is processed by emWeb, the placeholder will be exchanged for the output of a custom application code.

Virtual filesVirtual files allow to deliver complete pages that are built when they are requested. Typical examples are XML files that represent the current state of an application and are therefore subject to change for almost every request.
AJAX

AJAX is an acronym for Asynchronous JavaScript and XML. Together with browser DOM (Document Object Model) support, it allows dynamic modification of a page without requiring to reload the complete page.

To request data, with AJAX the browser needs to poll for data.

SSE

Unlike AJAX, Server-Sent Events (SSE) are an HTML5 technique that allows a server to send data to the browser, without the browser permanently polling for data and therefore reducing unnecessary data overhead.

SSE works by the browser subscribing to the Web server and keeping the connection up for further data sent.

 

Dynamic page samples

Authentication

emWeb supports the following authentication mechanisms.

AuthenticationDescription
Basic

As the name implies, the Basic Authentication scheme is a very simplistic mechanism for access control, in terms of security. The user name and password are transmitted in clear text.

While it is insecure by its design, it is still in use as SSL/TLS security in modern applications strengthen the underlying layers.

DigestThe Digest Authentication scheme uses an MD5 based challenge/response handshake including nonce data. The password is never sent in clear text, which makes it a good choice in case a lightweight and secure authentication is required where SSL/TLS is not possible.


Form handling

emWeb supports both, POST and GET methods to receive form data from a client. An easy to use application API allows to retrieve and process form data in a simple and memory efficient way.