# Simulator (3.x)

Warning

Beginning with v3.9.0 and ending with v4.0.0 this simulator will be replaced by a new version.

The simulator is a full fledged modbus simulator, which is constantly being evolved with user ideas / amendments.

The purpose of the simulator is to provide support for client application test harnesses with end-to-end testing simulating real life modbus devices.

The datastore simulator allows the user to (all automated)

- simulate a modbus device by adding a simple configuration,

- test how a client handles modbus exceptions,

- test a client apps correct use of the simulated device.

The web interface allows the user to (online / manual)

- test how a client handles modbus errors,

- test how a client handles communication errors like divided messages,

- run your test server in the cloud,

- monitor requests/responses,

- inject modbus errors like malicious a response,

- see/Change values online.

The REST API allow the test process to be automated

- spin up a test server with unix domain sockets in your test harness,

- set expected responses with a simple REST API command,

- check the result with another simple REST API command,

- test your client app in a true end-to-end fashion.