Communicate with PLCs Easily

Connect to PLCs and any other MODBUS devices using a simple but powerful HTTP API
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Features communication to Modbus field devices and providing and HTTP API to HMI clients.

How Unserver Works

Unserver communicates to field devices via Modbus protocol and provides an HTTP API to higher-level clients.

Unserver HTTP API provides essential data acquisition features, such as grouping Modbus addresses into tags, data caching, continuous polling and data type conversion

Any language or platform can use Unserver API to communicate with Modbus networks and devices easily.

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You don't have to learn Modbus or OPC UA. Simply use this clean and well documented API to easily create your HMI or data acquisition projects.


Create a data model using Tags. Achieve top peformance with data Caching and Polling supported out of the box.


Unlike many other communication technologies, Unserver is designed with the requirement of being lightweight, easy to install, configure and and use.


Integrating modern Web Applications with PLCs have never been easier. With Unserver REST API making a basic Web HMI takes minutes!

Configuration is performed in JSON files. Unserver automatically creates HTTP endpoints to read and write Modbus data using tags.

Clean and Simple

It's really easy to work with Unserver. All you need to know is how to edit JSON configuration files and how to make HTTP calls!

As you can see on the image, tags are defined in a JSON file (at the top) and the web browser is displaying the tag's value below.

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A demostration of a Web HMI screen integrated with Unserver API


Unserver is ready to be used as a back-end for Web Applications and Web HMI development.

It provides a RESTful API to read and write Tags, which simplifies the integration of PLCs and other Modbus devices with Javascript code.

Unserver includes a Demo Web App which shows how a web front-end can connect to Unserver.

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Examples of JSON files used to configure Unserver, creating tags and HTTP API.

Use simple JSON files for configuration

In this example a tag defined in tags.json represents the state of a field device. Unserver will read this configuration to understand where the data is located and how to interpret it.

Unserver will automatically create HTTP endpoints that you can use to read and write the value of the tag.

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To install Unserver, simply extract the package anywhere.


Edit the config files to create a tag and specify communication settings.


Start Unserver. Now the HTTP API is up and ready!