Getting started

Start here

Use this page for your first KEYENCE KV Host Link read and write from Node-RED. The examples below use 192.168.250.100:8501.

Prerequisites

Requirement	Value
Node.js	18 or newer
Node-RED	3.0 or newer
PLC endpoint	192.168.250.100:8501
Transport	TCP unless your PLC setup requires UDP

Install

Step	Action
1	Open Node-RED.
2	Open Manage palette.
3	Choose Install.
4	Search for @fa_yoshinobu/node-red-contrib-plc-comm-kvhostlink.
5	Install the package and restart Node-RED if prompted.

Choose profile

The connection node requires an exact canonical PLC profile string. Start with the profile that matches your KV family.

PLC family	Profile to select
KEYENCE KV-3000	keyence:kv-3000 or keyence:kv-3000-xym
KEYENCE KV-5000 family	keyence:kv-5000 or keyence:kv-5000-xym
KEYENCE KV-7000 family	keyence:kv-7000 or keyence:kv-7000-xym
KEYENCE KV-8000	keyence:kv-8000 or keyence:kv-8000-xym
KEYENCE KV-X500 family	keyence:kv-x500 or keyence:kv-x500-xym
KEYENCE KV-NANO	keyence:kv-nano or keyence:kv-nano-xym

Create a connection node

Add or edit a kvhostlink-connection config node.

Field	Example value	Description
Name	KV Host Link TCP	Display name in the editor.
Host	192.168.250.100	IP address or host name for your PLC.
Port	8501	Explicit PLC endpoint port. The editor initially displays the commonly used Host Link port.
Transport	tcp	Use tcp or udp.
Timeout	3000	Response timeout in milliseconds.
PLC Profile	keyence:kv-5000	Exact canonical profile value for your PLC.

Import the basic flow

Step	Action
1	Open the Node-RED import menu.
2	Import examples/flows/kvhostlink-basic-read-write.json.
3	Confirm the connection node uses host 192.168.250.100, port 8501, and your canonical PLC profile.
4	Deploy.
5	Trigger Read DM100:U.
6	Check the debug sidebar for a value.

Read your first value

For a single manual read, configure a kvhostlink-read node like this:

Field	Value
Connection	Your kvhostlink-connection node
Source	str
Addresses	DM100:U
Output	Single value when one address
Metadata	Minimal msg.kvhostlink
Errors	Second output

Successful output is written to msg.payload.

{
  "payload": 123
}

Read a device comment

An address such as DM145:COMMENT uses the Host Link RDC command. The read node requires an explicit RDC comment selection before it connects:

• Choose Decoded text, then select exactly UTF-8 or CP932 / Windows-31J.
• Choose Raw Buffer when the stored encoding is unknown or bytes must be preserved exactly.

KEYENCE material may call Windows-31J-compatible data “Shift_JIS”; this library names that selection cp932 and does not expose a separate strict Shift_JIS mode. It never guesses from bytes or PLC profile, retries another codec, or inserts replacement characters for malformed input.

First write

For a single manual write, configure a kvhostlink-write node like this:

Field	Value
Connection	Your kvhostlink-connection node
Source	str
Static updates	{"DM100:U":123}
Metadata	Minimal msg.kvhostlink
Errors	Second output

Use only a test address that is safe for your machine and PLC program. The table above shows the write-node input shape; it does not by itself provide a restore sequence. The imported starter flow provides the safer demonstration: Test DM100:U (random + restore) reads and saves the original value, writes a random different unsigned value, restores the saved value, and reads again. Restoration is best effort and cannot be guaranteed if the PLC or connection fails during the sequence, so use only a controlled test address.

Confirm success

Check	Expected result
Connection status	The connection node status changes to connected during the request.
Read status	The read node reports 1 item(s).
Debug output	The debug sidebar shows msg.payload.
Error output	The error output stays quiet.
Write path	The optional starter-flow path writes a random valid value only after saving the original.
Restore readback	The final read shows the restored original value.

If it does not work

Symptom	Check
Timeout immediately	Confirm the explicitly saved port; Host Link commonly uses 8501, not SLMP port 1025.
Profile dropdown rejects a value	Use only the exact values in PLC profiles.
First import feels too large	Import kvhostlink-basic-read-write.json first, not the device-matrix flow.
Timer/counter preset write fails	Timer/counter preset writes only work on KV-8000/7000-series CPU units.
Transport fails	Check that your PLC Host Link setting allows the selected TCP or UDP transport.