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Message Dispatch is Devset’s built-in request tool for sending individual messages to a Kafka topic or a RabbitMQ queue or exchange. Think of it as a Postman-style client purpose-built for event brokers — you compose a payload, attach a schema for validation or encoding, and fire it off against any configured connector. Open Message Dispatch at http://localhost:8082/message-dispatch.

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Sending a Message

1

Select a connector

At the top of the request card, open the Connector dropdown and choose the Kafka or RabbitMQ connector you want to send through. Connectors are the named broker connections configured in your Devset instance.
2

Set the target

Enter the destination for your message. The fields shown depend on the broker type:
Enter the Topic name you want to publish to.Optionally configure:
  • Key — the Kafka message key used for partition routing.
  • Headers — additional key-value metadata attached to the message envelope.
3

Compose the payload

Write your message payload in the Payload Editor. You can switch between two modes:
  • Raw JSON — type or paste a JSON object directly.
  • Function Studio — use dynamic field expressions (see the Flow Builder guide for an overview of expression modes such as FN, REF, and WHEN).
Here is an example raw JSON payload:
{
  "orderId": "ord-8821",
  "customerId": "cust-0042",
  "items": [
    { "sku": "WIDGET-A", "qty": 3 },
    { "sku": "WIDGET-B", "qty": 1 }
  ],
  "total": 149.99,
  "currency": "USD"
}
4

Attach a schema (optional)

In the Schema section of the request card, select a schema ID from the Schema Repo. Devset uses the schema to validate JSON payloads before sending, or to encode Protobuf payloads into binary wire format. Configure Wire Format settings if you are using Protobuf.
5

Send the message

Click Send. Devset dispatches the message to the broker through the selected connector. The result appears in the History panel.

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Organizing Requests with Collections

Collections are named groups of saved requests. They let you organize related messages — for example, all messages related to an order lifecycle — and re-send them quickly without re-filling the form.
1

Save a request

After composing a request, click Save. The save modal prompts you for a name and a collection. Choose an existing collection or type a new name to create one.
2

Open a saved request

In the Collections panel on the left, expand a collection and click any saved request to load it back into the request card.
3

Re-send or modify

Adjust any fields as needed and click Send again. Saving again overwrites the existing entry or creates a new one depending on your choice in the save modal.
Use collections to build a library of test fixtures for each of your event schemas. Pair them with the Schema Repo so every request has a schema attached and payload validation runs automatically before dispatch.

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Attaching a Schema for Validation and Encoding

The Schema section of the request card connects a dispatch request to a definition in the Schema Repo.
  • JSON Schema — Devset validates the payload structure before sending. Validation errors surface inline in the payload editor.
  • Protobuf — Devset encodes the JSON object into binary Protobuf format using the linked .proto definition before placing the message on the broker. Configure the Wire Format options to match your consumer’s expectations.
Select the schema from the dropdown in the Schema section. The schema ID displayed here matches the schemaId you assigned when creating the schema in the Schema Repo.

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Reviewing Past Dispatches

The History panel on the right side of the screen logs every message you have sent in the current session. Each entry shows the connector, target, and a timestamp. Click any history entry to open a preview modal showing the full request details — connector, target, headers, and the exact payload that was sent. This is useful for confirming what was dispatched and for debugging unexpected broker behavior.
History is session-scoped. Refreshing the page clears the history panel. Save any requests you want to keep to a collection before closing the tab.