ZeroMQInstall

Overview

This node enables sending and receiving messages using ZeroMQ sockets, a high-performance asynchronous messaging library. It supports various socket types such as Request-Reply, Publish-Subscribe, Push-Pull patterns, allowing flexible communication setups.

The Receive operation listens for incoming messages on specified ZeroMQ socket types (pull, sub, or rep). It can act either as a server (bind) or client (connect) to a given socket address. For subscription sockets, it supports filtering by topic. For reply sockets, it automatically sends a configured response after receiving a message.

Use cases:

• Receiving task messages from distributed workers via Pull sockets.
• Subscribing to published events filtered by topic.
• Implementing request-reply patterns where the node replies automatically upon receiving requests.

Properties

Output

The node outputs an array of JSON objects representing received messages. The structure depends on the socket type:

• Subscribe (SUB):

  {
    "topic": "<received_topic>",
    "message": "<received_message>"
  }
  

  • topic: The topic string of the received message.
  • message: The message content following the topic.

• Pull (PULL):

  {
    "message": "<received_message>"
  }
  

  • message: The received message content.

• Reply (REP):

  {
    "message": "<received_message>"
  }
  

  • message: The received request message. The node automatically sends back the configured response.

No binary data output is produced by this node.

Dependencies

• Requires the zeromq Node.js package for ZeroMQ socket communication.
• No special n8n credentials are required, but the node needs network access to the specified ZeroMQ socket addresses.
• Ensure that the ZeroMQ environment (servers or peers) is properly set up and accessible.

Troubleshooting

• Invalid socket type error:
  If you select a socket type not supported for the Receive operation (only pull, sub, and rep are valid), the node will throw an error. Make sure to choose a compatible socket type.

• Connection issues:
  Binding or connecting to an invalid or unreachable socket address will cause errors or timeouts. Verify the socket address format and network connectivity.

• Subscription topic filtering:
  If no messages are received on a Subscribe socket, check if the topic filter matches the published topics. Leaving the topic empty subscribes to all messages.

• Automatic response in Reply socket:
  The node sends a fixed response after receiving a message on a Reply socket. If the peer expects a different protocol or response, communication may fail.

• Resource cleanup:
  The node closes the socket after receiving one message. For continuous listening, consider looping or triggering the node repeatedly.

Links and References

• ZeroMQ Official Documentation
• ZeroMQ Socket Types
• n8n Custom Nodes Documentation