Skip to content

Network & Communication Nodes

Nodes for industrial protocols, TCP/IP communication, and media streaming.

Modbus TCP

Modbus TCP is an industrial protocol widely used in building automation, PLCs, and SCADA systems. The Flow provides a complete set of nodes to connect to Modbus TCP servers and read/write various data types.

Modbus TCP Client

The Modbus TCP Client node establishes and manages a connection to a Modbus TCP server.

Category: Network, Modbus

Functionality

Creates a persistent connection to a Modbus server. Other Modbus nodes use the Conn Key output to share this connection.

Inputs

Name Type Description
Connect Boolean Rising edge opens the connection; falling edge closes it

Outputs

Name Type Description
Connected Boolean True while connection is active
Conn Key String Unique key to pass to read/write nodes

Properties

  • Host: IP address or hostname of the Modbus server (e.g., 192.168.1.100)
  • Port: TCP port (default: 502)
  • Slave ID: Modbus slave/unit ID (default: 1)

Tip

Keep one TCP Client node and wire its Conn Key to multiple read/write nodes. This shares the connection efficiently.

Modbus Write Coil

Writes a boolean value to a single coil register.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Write Boolean Rising edge triggers the write
Value Boolean The value to write (ON/OFF)

Outputs

Name Type Description
Written Boolean Pulses true when write completes

Properties

  • Address: Coil address (0-65535)

Modbus Read Coil

Reads a boolean value from a single coil register.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Read Boolean Rising edge triggers the read

Outputs

Name Type Description
Read Boolean Pulses true when read completes
Value Boolean The coil state

Properties

  • Address: Coil address (0-65535)

Modbus Write Int

Writes a 16-bit integer value to a holding register.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Write Boolean Rising edge triggers the write
Value Integer The value to write (-32768 to 32767)

Outputs

Name Type Description
Written Boolean Pulses true when write completes

Properties

  • Address: Holding register address (0-65535)

Modbus Read Int

Reads a 16-bit integer value from a holding register.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Read Boolean Rising edge triggers the read

Outputs

Name Type Description
Read Boolean Pulses true when read completes
Value Integer The register value

Properties

  • Address: Holding register address (0-65535)

Modbus Write Float

Writes a 32-bit IEEE 754 floating-point value to two consecutive holding registers.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Write Boolean Rising edge triggers the write
Value Float The floating-point value

Outputs

Name Type Description
Written Boolean Pulses true when write completes

Properties

  • Address: Starting holding register address (uses 2 registers)

Modbus Read Float

Reads a 32-bit IEEE 754 floating-point value from two consecutive holding registers.

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Read Boolean Rising edge triggers the read

Outputs

Name Type Description
Read Boolean Pulses true when read completes
Value Float The floating-point value

Properties

  • Address: Starting holding register address (uses 2 registers)

Modbus Write String

Writes a string to multiple holding registers (2 ASCII characters per register).

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Write Boolean Rising edge triggers the write
Value String The text to write

Outputs

Name Type Description
Written Boolean Pulses true when write completes

Properties

  • Address: Starting holding register address
  • Length: Maximum string length (number of registers = length / 2)

Modbus Read String

Reads a string from multiple holding registers (2 ASCII characters per register).

Category: Network, Modbus

Inputs

Name Type Description
Conn Key String Connection from Modbus TCP Client
Read Boolean Rising edge triggers the read

Outputs

Name Type Description
Read Boolean Pulses true when read completes
Value String The retrieved text

Properties

  • Address: Starting holding register address
  • Length: Number of characters to read

Modbus Example

A typical Modbus setup:

  1. Add a Modbus TCP Client node and configure the server IP and port
  2. Wire an Enable node or trigger to the Connect input
  3. Add Modbus Read/Write nodes and connect their Conn Key input to the client's output
  4. Use timers or triggers to control when reads/writes occur

Warning

Ensure the Modbus server is accessible from the camera network. Firewall rules may need adjustment.

Media Streaming

WebRTC Stream

The WebRTC Stream node streams video from an Axis device over WebRTC protocol.

Category: Axis, Network

Functionality

Enables real-time video streaming with low latency. Supports both LAN connections and TURN/STUN for NAT traversal.

Properties

  • Device: Select the Axis device from Device Management
  • Resolution: Optional resolution override
  • TURN/STUN: Configure relay servers for remote access

Tip

WebRTC provides lower latency than RTSP for interactive applications.

RTMP Stream

The RTMP Stream node publishes video to RTMP media servers or streaming platforms.

Category: Axis, Network

Functionality

Streams the camera feed to YouTube Live, Twitch, or custom RTMP servers.

Inputs

Name Type Description
Publish Boolean True starts streaming; false stops

Properties

  • Device: Select the Axis device
  • RTMP URL: Server URL (e.g., rtmp://a.rtmp.youtube.com/live2)
  • Stream Key: Authentication key for the platform
  • Resolution: Video resolution to stream

Warning

Streaming uses significant bandwidth. Ensure adequate upload capacity.

TCP Communication

TCP Server

Listens on a TCP port and outputs received messages.

Category: Input, Network

Outputs

Name Type Description
New Message Boolean Pulses true when data arrives
Message String The received payload

Properties

  • Port: TCP port to listen on (1-65535)
  • Rate Limit: Maximum messages per second

TCP Message Sender

Sends string payloads over TCP to a remote host.

Category: Action, Network

Inputs

Name Type Description
Send Boolean Rising edge sends the message
Message String Payload to transmit

Outputs

Name Type Description
Sent Boolean Pulses true on success

Properties

  • Host: Destination IP or hostname
  • Port: Destination port
  • Timeout: Connection timeout in seconds

HTTP & Webhooks

Webhook Listener

Runs an HTTP/HTTPS endpoint to receive external requests.

Category: Input, Network

Inputs

Name Type Description
Custom Response Boolean Enable custom response body
Response Body String Custom JSON response
Response Code Integer HTTP status code to return

Outputs

Name Type Description
New Request Boolean Pulses true on each request
Body String Request body content
Query params String One output per configured parameter

Properties

  • Port: HTTP or HTTPS port
  • Path: URL path (e.g., /webhook)
  • Auth Type: None, Basic, or Digest
  • Rate Limit: Requests per second (1-15)
  • Query Parameters: Define expected URL parameters

The webhook always responds with: 

{"success": true, "message": "OK"}

Unless custom response is enabled.

Tip

Use query parameters to pass identifiers like device_id or event_type without parsing the body.