LabVIEW™ WebSockets API / Library

Connecting LabVIEW™ to the Web for custom HTML/JavaScript dashboards

Introduction

The LabVIEW WebSockets API library allows a web browser to communicate with a LabVIEW™ application acting as a WebSocket server. Web Sockets offers low-latency communications between a LabVIEW™ application and a web browser with no plug-ins or LabVIEW™ run-time engine installation requirements.

It contains VIs for performing WebSockets handshaking, reading/writing data and closing the connection. The API allows code to be written for your LabVIEW™ application to act as both a Web Sockets server (e.g. communicate with a browser), and as a client (e.g. to talk to existing WebSockets services).

As it uses the native TCP/IP VIs in LabVIEW™, it works on both desktop LabVIEW™ (e.g. Windows, Linux etc.) and also LabVIEW™ RT (e.g. CompactRIO, sbRIO etc.).

The library is ideal for communicating between a LabVIEW™ NXG WebVI and a LabVIEW application – allowing you to create responsive web-based user interfaces for your applications using LabVIEW NXG – no HTML/CSS/JavaScript coding knowledge required!

MediaMongrels Ltd has extensive experience of using this library to create dynamic web-based user interfaces for LabVIEW™ applications. If you would like to use our services to incorporate the library into your application, please contact us to discuss your requirements.

Links / Examples

WebSockets API on the LabVIEW™ Tools Network

Uses

Custom User Interfaces: The WebSockets library allows embedding of a user interface written in HTML/JavaScript directly into LabVIEW™ applications. This opens up the possibility of using a wide variety of graphing and UI toolkits within applications as well as better support for varying screen sizes/resolutions.
Communication between WebVIs and LabVIEW applications: WebSockets offers a low-latency and asynchronous communications method between a WebVI and a LabVIEW application. WebSockets client support is available in NXG WebVIs since version 3.1.
Remote Monitoring: Enabling LabVIEW™ applications with WebSockets allows communication with an application running remotely over a LAN (or WAN/VPN) network. This would allow monitoring/control of applications running in a remote environment (e.g. in a lab/workshop/production area) from the office.
LabVIEW™ RT / Embedded User Interfaces: Using WebSockets on an RT Target (such as an sbRIO / CompactRIO), stylish user interfaces can be created for embedded targets or products.
Mobile Interfaces: Most modern smartphones support the WebSockets protocol, allowing bespoke user interfaces for monitoring/control of LabVIEW™ applications from a mobile device such as a phone or tablet.
Multi-User Interfaces: The WebSockets server can support multiple simultaneous clients, allowing multiple users to interface with the application at the same time.

Download / Installation

The library is published as a VI Package on the NI Tools Network – it can be found in the NI Tools Network repository in VIPM or installed by clicking the link below.

INSTALL NOW (using VIPM)

LabVIEW WebSockets API on the NI Tools Network

Source Code – GitHub Repository

The VI Package is supported in LabVIEW™ 2013 or later.

Support

Support for the LabVIEW WebSockets API is provided via the project GitHub page.

For advanced support and implementation/application help – please contact us to discuss paid support options.

Usage / Licensing

The package/source is released under the MIT License. You will be asked to read/accept the license when installing the VI Package.

Documentation

As of version 2.X onwards, the VI Package includes comprehensive help documentation (available from the LabVIEW™ tools menu) and basic examples of a WebSocket server communicating with a HTML/JavaScript based web-page and a client example for communicating with a 3rd party WebSockets server.

LabVIEW™ users familiar with the TCP/IP VIs should have no problems integrating the WebSockets API into their applications. The library is a wrapper for the native functions and usage is similar. A simple example of how to use the library is shown below, along with a description of each VI.

WebSockets Server

The library supports acting as a WebSockets Server. This allows you to write LabVIEW™ that can communicate with a WebSockets client such as a web-browser.

WebSockets API Server Example in LabVIEW

WebSockets Client

The library also supports acting as a WebSockets Client. You can use the WebSockets Client functionality to talk to a 3rd party WebSockets Server (ws:// only) with LabVIEW™.

WebSockets Client API

Function Overview

New / Upgrade: Opens a new WebSockets connection as a client or upgrades an existing Socket connection to a WebSockets connection.
Handshake: Performs the WebSocket handshaking after a connection is made – reads the headers from the HTTP request and replies with the appropriate WebSocket key to open the connection. Performs the appropriate handshake depending on whether the it is a server or client connection.
Get / Set Header: Sets a send header or reads a header returned from the client/server.
Read Text / Binary: Reads a text or binary frame from the WebSockets connection. Automatically handles Ping/Pong frames and multi-frame messages.
Write Text / Binary: Writes a text or binary frame to the WebSockets connection.
Close: Sends the WebSocket close frame and closes the connection.

Changelog

V2.0.0.38 (05/09/2019)
Major rewrite of the WebSockets library:
– New: Moved library to an OO approach for WebSockets connections (Client/Server Classes)
– New: Abstracted underlying socket functionality (e.g. NI VISA TCP) for future secure WebSockets support
– New: Added TCP socket listener for listening for server socket connections
– New: Simplified API
– New: Added high-level Read function which internally handles fragmented and Ping frames
– New: Added WebSockets Client Example VI and modified examples to use new classes
– New: Added unit testing to source repository
– New: Added detailed documentation (.chm file) to LabVIEW Help menu and added examples to NI Example Finder
– New: Added palette support for LV2020
– Fix: Fixed incorrectly applied timeout values (timeout = approx. maximum time until VI returns)
– Fix: WebSocket-Client-Key is now correctly generated as a random string rather than being a constant

Note: A backwards compatibility layer is retained for legacy applications allowing upgrade with minimal application changes. It is strongly recommended to update applications to use the new library VIs. See the built-in help documentation for more information.
V1.6.0.22 (19/10/2016)
The package has now been released on the NI LabVIEW™ Tools Network package repository. This and future versions will be available directly through VIPM (vipm://mediamongrels_ltd_lib_websockets_api).
Changes in this version include:
– Fixed an issue with the incorrect EOL being used in InitiateClientHandshake.vi for better cross-platform support.
– Added support for sending additional headers in the client handshake / server response
– Added support for Sec-WebSocket-Protocol: The DoHandshake.vi now has a ‘supported protocols’ input which allows supported protocols to be listed (in order of preference). This will increase compatibility with existing WebSocket servers.
– The package is now released under the MIT License
Note: The VI package has also changed name. Please uninstall any previous versions of this package before upgrading.
V1.3.0.13 (20/04/2015)
– Added functionality to be able to act as a WebSockets client – incoming/outgoing messages are now de-masked correctly and optionally masked for transmission. Added VI for creating & sending the HTTP handshake. This WS client functionality has not been fully tested (e.g. with external WS servers) but has been tested with a LabVIEW™ server using my library.
V1.2.0.9 (04/02/2015)
– Made mask values more clear in source and updated calculation of message length bytes. (Thanks Stuart)
V1.1.2.8 (14/01/2015)
– Fixed an error in accepting the request due to casing of the initial HTTP headers sent by IE.
– Fixed the javascript example throwing an error in Firefox. (Thanks Martin)
V1.1.1.7 (19/12/2014)
– Fixed an error in DoHandshake that was causing the VI to finish only on timeout instead of at the end of the HTTP header (causing connections to take longer than required).