Node-RED Siemens S7 PLC Communication

1.1.6 · active · verified Sun Apr 19

node-red-contrib-s7comm is a Node-RED package designed to facilitate communication with Siemens SIMATIC S7-300, S7-1200, and S7-1500 PLCs. It leverages the RFC1006 (ISO-on-TCP) communication protocol, enabling users to read from and write to specific PLC addresses using various S7 data types. The current stable version is 1.1.6. As a Node-RED contribution node, its release cadence is typically driven by community contributions and updates to its underlying `nodeS7` library, which handles the core PLC communication. Key differentiators include its integration into the Node-RED flow-based programming environment, simplifying the creation of HMI, SCADA, or IIoT applications that interact with Siemens PLCs without requiring extensive low-level protocol knowledge. It abstracts the complexities of the S7comm protocol behind user-friendly Node-RED nodes.

Common errors

```
Error: Connection refused
```
cause The PLC rejected the connection attempt, often due to incorrect IP, port, firewall blocking, or PLC security settings.

fix Verify the PLC's IP address and port (default 102), check network connectivity between Node-RED host and PLC, ensure no firewall is blocking port 102, and confirm PLC 'Protection & Security' settings allow PUT/GET communication.
```
Error: S7 response data error - wrong data size
```
cause The configured data length or type in the Node-RED node does not match the actual data block/variable size on the PLC.

fix In the Node-RED node's configuration, precisely match the S7 data type (e.g., INT, REAL) and length to what is defined in the TIA Portal for the target PLC address (DB, address, size).
```
Error: S7 PLC response: 10/FF00
```
cause Generic PLC communication error, frequently indicating that the PLC's security settings prevent access to the requested data block or an unsupported access method.

fix Check the PLC's 'Protection & Security' settings in TIA Portal for PUT/GET permissions. For data blocks, ensure 'Optimized block access' is not solely enabled if the client expects standard access, or vice-versa, and verify block attributes.
```
TypeError: Cannot read properties of undefined (reading 'config')
```
cause This error typically occurs within Node-RED when a node's associated configuration node (e.g., the S7comm-Config node) is either missing, unlinked, or not properly deployed.

fix Ensure that your 's7comm read' or 's7comm write' node is correctly linked to an 's7comm-config' node, and that the 's7comm-config' node is also properly configured. Perform a 'Full deploy' in Node-RED after making changes.

Warnings

gotcha Siemens S7-1200/1500 PLCs require specific 'Protection & Security' settings in TIA Portal (e.g., 'Permit access with PUT/GET communication from remote partner') to allow external read/write access via S7comm. Failure to configure this will result in connection refusal.
Fix: In TIA Portal, navigate to the PLC properties, then 'Protection & Security', and enable 'Permit access with PUT/GET communication from remote partner (PLC, HMI, OPC)'.
gotcha Incorrect S7 data type or length configuration in the Node-RED node can lead to read/write errors, corrupted data, or unexpected values. The node expects precise mapping to the PLC's actual data block structure.
Fix: Always cross-check the configured S7 data type (e.g., BYTE, WORD, INT, REAL, BOOL) and array length in the Node-RED node against the PLC's TIA Portal project variables for exact matches.
gotcha Node-RED flow deployments, especially involving configuration nodes, must be handled carefully. Partial or incorrect deployments can result in nodes remaining uninitialized or losing their connection settings.
Fix: After making changes to S7comm nodes or their configuration nodes, perform a 'Full deploy' in Node-RED to ensure all nodes are correctly initialized with the latest settings. Check the Node-RED debug tab for errors.
gotcha The stability and security of `node-red-contrib-s7comm` are dependent on the underlying `nodeS7` library. Any vulnerabilities or critical bugs discovered in `nodeS7` will directly impact this Node-RED contribution.
Fix: Monitor the GitHub repositories for both `node-red-contrib-s7comm` and `nodeS7` for updates and security advisories. Ensure you are running the latest stable versions of both.

Install

npm install node-red-contrib-s7comm npm
yarn add node-red-contrib-s7comm yarn
pnpm add node-red-contrib-s7comm pnpm

Imports

S7CommNode
```
/* This package is a Node-RED node. Users do not typically import symbols directly into JavaScript. */
```
As a Node-RED contrib package, this node is primarily configured and used within the Node-RED flow editor. Direct programmatic JavaScript/TypeScript `import` statements for users are not the intended interaction method. The entries here are illustrative of what internal components *might* be exposed if it were a standard library, but are not for typical user consumption.
S7ConfigNode
```
/* This package is a Node-RED node. Users do not typically import symbols directly into JavaScript. */
```
Configuration nodes for Node-RED are managed by the runtime and exposed via the editor's palette. Users define instances of these nodes graphically.
S7Client
```
/* This package is a Node-RED node. Users do not typically import symbols directly into JavaScript. */
```
While an underlying S7 client (from `nodeS7`) is used internally, it is not directly exposed for programmatic import by users of `node-red-contrib-s7comm`. Interaction is abstracted through Node-RED's message passing system.

Quickstart

Illustrates the typical installation process for Node-RED packages via the Palette Manager and provides a conceptual JavaScript snippet for direct S7 client interaction (not directly from this Node-RED node).

// To install the Node-RED node:
// 1. Ensure Node-RED is installed and running.
// 2. Open the Node-RED editor (usually http://localhost:1880).
// 3. Go to the Palette Manager (top-right menu -> Manage palette).
// 4. In the 'Install' tab, search for 'node-red-contrib-s7comm' and click install.

// After installation, drag 's7comm read' and 's7comm write' nodes from the palette onto your flow.
// Example JavaScript code showing conceptual S7 client usage, not direct 'node-red-contrib-s7comm' usage:

// import { S7Client } from 'nodeS7'; // Hypothetical import if using nodeS7 directly

// async function readS7Data() {
//   const client = new S7Client();
//   try {
//     await client.connect({
//       host: '192.168.0.1',
//       port: 102,
//       rack: 0,
//       slot: 1
//     });
//     console.log('Connected to PLC.');

//     const data = await client.readArea(
//       S7Client.S7Area.DB,
//       1, // DB number
//       0, // Start offset
//       2, // Length (e.g., 2 bytes)
//       S7Client.S7Type.WORD
//     );
//     console.log('Read data:', data);
//   } catch (error) {
//     console.error('S7 communication error:', error);
//   } finally {
//     client.destroy();
//   }
// }

// readS7Data();

view raw JSON →