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Minnow Server

Minnow Server, a super small and fast embedded HTTPS (secure) WebSocket server, lets small microcontrollers with no external memory act as real-time web servers. The super small and secure Minnow Server is ideal for devices that are too small for standard web applications or our Barracuda Embedded Web Server.

How does Minnow Server work?

Minnow Server incorporates the HTML5 WebSocket specification, letting JavaScript applications open a persistent, bidirectional, full-duplex and asynchronous communication channel with the embedded device. The Minnow Server is specifically designed to facilitate the use of modern Single Page Applications (SPA) for device management and can be used with modern frameworks such as AngularJS, ReactJS, and Vue.js.

Real-Time Web Server for Tiny Microcontrollers

Minnow ServerThe Minnow Server is ideal for most modern microcontroller-based systems, enabling you to web-enable even the tiniest device.

Web applications for Minnow Server are designed in JavaScript and can load on demand from the device, the browser’s local file system, directly from a browser, such as a Chrome browser app or a cloud server.

You decide where to store the web presentation logic by selecting one or all of the above options. Of course, the benefit of storing the web presentation logic off device is that it saves considerable space on the device and lets you easily modify the application without upgrading the firmware.

The Minnow Server is primarily designed for small micro controllers such as the Cortex-M3/M4 family, where internal memory is limited and using a full application server, such as the Barracuda Application Server, is not an option. Minnow Server is not recommended for larger embedded systems, where a full application server can fit into the memory.

Optional ZIP File System Plugin

In addition to being a WebSocket server, Minnow Server includes an embedded HTTP server, which makes it possible for the browser to load the web presentation logic on demand from the device. Web presentation logic, including JavaScript, has a tendency to be large, so the data may be too big for your microcontroller’s flash memory. Real Time Logic provides an optional ZIP file-system plugin for the Minnow Server.

Compressed web applications are typically only one-third of the original size and are loaded on demand by the browser without needing to be uncompressed on the device. The web pages are extracted from within the ZIP file and sent “as is” to the browser which then uncompresses the data received from the server.

How the WebSocket Protocol Works

WebSocket Upgrade RequestThe WebSocket protocol defined in RFC 6455 specifies how a standard HTTPS request/response pair can be upgraded to a secure and persistent full-duplex connection. HTML5 WebSocket-based applications enable real-time communication while placing less burden on the servers.

WebSockets is a relatively new standard that brings real-time communication to the web. WebSockets is supported by all modern browsers and is designed to provide a persistent full-duplex asynchronous communication channel over a single TCP connection.

Most embedded web device management applications currently operate by simply responding to user interactions. You click a button and this causes the browser to submit the data to the server. The server performs the command and responds with a new HTML page. This old technology works, but it is a very limiting model. You may have moved beyond the simple GET/POST submit button web design concept and embraced AJAX/REST. However, the fact remains that AJAX is still a one way asynchronous message sent from the browser to the server and any real-time updates you want to display in the browser require polling of server resources. You may still think AJAX and REST are the way to go; however, the entire AJAX protocol could be built using Websockets technology. This makes Websockets literally a superset of AJAX so it makes sense that we might abandon a limiting technology for a broader technology.

The fact that Websockets provide a bi-directional communication channel between the browser and server immediately opens up some very interesting opportunities for web based device management applications. Because the connection is persistent, the embedded web server can now initiate communication with the browser. The embedded web server can send alerts, updates, notifications, etc.. This adds a whole new dimension to the types of web based device management applications that can be constructed.

About Real Time Logic

Real Time Logic is a world class IoT security and web-enablement specialist. Their solutions and Ecosystem Partners drive modern real-time embedded applications to ensure the smooth deployment and safe operation of next generation products. More details…

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