> For the complete documentation index, see [llms.txt](https://docs.augelab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.augelab.com/function-blocks/blocks-reference/input-output/communication/modbus-connect.md).

# Modbus Connect

This function block establishes a Modbus TCP connection to a remote device and provides a reusable `Modbus Client` output that other blocks can use to perform reads/writes.

## 📥 Inputs <a href="#inputs" id="inputs"></a>

This function block does not have any inputs.

## 📤 Outputs <a href="#outputs" id="outputs"></a>

`Modbus Client` A connected Modbus client reference that can be fed into communication blocks to read or write registers.

## 🕹️ Controls <a href="#controls" id="controls"></a>

`IP Address` Enter the Modbus TCP server IP address (for example 192.168.0.10).

`TCP Port` Enter the Modbus TCP port (default is commonly 502).

## ⚙️ Running mechanism <a href="#running-mechanism" id="running-mechanism"></a>

* When evaluated, the block attempts to connect to the Modbus server at the address and port provided in the controls.
* If the address or port is changed, or if the connection drops, the block will attempt to reconnect automatically and continues to provide an updated `Modbus Client` output for other blocks.
* Other blocks receive the `Modbus Client` through the output socket and use it to perform communication tasks (reads/writes).

## 🎯 Features <a href="#features" id="features"></a>

* Persistent connection output so multiple blocks can share a single client.
* Automatic reconnection when address changes or the connection is lost.
* Simple UI controls for IP and port configuration.

## 📝 How to use <a href="#usage" id="usage"></a>

1. Set the `IP Address` and `TCP Port` in the controls.
2. Let the scenario run — the block will establish the connection and provide the `Modbus Client` on its output.
3. Connect the `Modbus Client` output to communication blocks that require it (for example read/write blocks) to perform Modbus operations.

## 💡 Tips and Tricks <a href="#tips-and-tricks" id="tips-and-tricks"></a>

* To read data regularly, connect the `Modbus Client` output to the `Modbus Read` block and use a `Logic Input` or another trigger to control when reads happen.
* To write commands or values, feed the `Modbus Client` to the `Modbus Write` block and use a logic trigger to perform writes only when needed.
* Forward telemetry to remote systems by combining with `MQTT Publish` (connect output from a read block into `MQTT Publish`) for lightweight messaging.
* Save or log values by sending read outputs into `SQL-DB Operations` or `CSV Export` for persistent storage and later analysis.
* Use `Debug Input` or `Scope` to inspect values coming from read blocks during setup and troubleshooting.

(hint: recommended companion blocks — `Modbus Read`, `Modbus Write`, `Logic Input`, `MQTT Publish`, `SQL-DB Operations`, `CSV Export`, `Debug Input`, `Scope`)

## 🛠️ Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* Connection refused or timeouts — check the `IP Address` and `TCP Port` are correct and that the Modbus server is reachable on the network.
* Firewall or network rules — ensure the port used for Modbus TCP is allowed through firewalls on both ends.
* Multiple clients — if the server limits connections, avoid creating many simultaneous connections; share the provided `Modbus Client` output with other blocks.
* If connection appears unstable, verify the network quality and try a different network cable or switch port.