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How To Use Websocket In Postman

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Understanding WebSockets and Postman

WebSockets provide a persistent, full-duplex communication channel between a client and server. This allows for real-time data exchange, unlike traditional HTTP requests which are typically one-way. Postman, a popular API testing tool, can be used to effectively test and interact with WebSocket endpoints.

Setting Up a WebSocket Request in Postman

  1. Navigate to the WebSocket Tab:

    • Open a new Postman request window.
    • Select the “WebSocket” tab located at the top.

  2. Configure the WebSocket Endpoint:

    • In the “URL” field, enter the WebSocket endpoint URL.
    • Select the “Type” of the request from the dropdown (e.g., “ws” for secure connections).

  3. Connect and Send Messages:

    • Click the “Connect” button.
    • Use the “Send” button to send messages to the server.
    • You can send plain text, JSON objects, or custom data formats.
    • Postman will display any server responses in the “Responses” tab.

Example:

// Send a JSON message to the WebSocket endpoint
{
  "message": "Hello from Postman!"
}

Working with WebSocket Events in Postman

Postman allows you to subscribe to and manage WebSocket events. These events can be used to receive notifications, handle errors, and more.

  1. Subscribe to Events:

    • In the “Events” section of the WebSocket tab, you can subscribe to specific WebSocket events:
      • Open: Triggered when a WebSocket connection is established.
      • Message: Triggered when a message is received from the server.
      • Close: Triggered when the WebSocket connection closes.
      • Error: Triggered when an error occurs in the connection.

  2. Manage Event Handlers:

    • Postman provides built-in event handlers for each WebSocket event. You can configure these handlers by clicking on the respective event in the “Events” section.
    • You can customize the event handler scripts to perform actions based on the triggered event.

Example:

//  Example "Message" event handler
pm.test("Verify message content", function () {
  var message = pm.response.text();
  pm.expect(message).to.contain("Response");
});

Sending and Receiving Multiple Messages in Postman

Postman supports sending multiple messages to a WebSocket endpoint. You can also configure it to receive multiple messages from the server.

  1. Sending Multiple Messages:

    • Within the “Send” field, you can enter multiple messages separated by newlines.
    • You can also use the “Send Multiple” button to send messages in a loop.

  2. Receiving Multiple Messages:

    • The “Responses” tab will display all the messages received from the server chronologically.
    • You can use the “Message” event handler to process individual incoming messages.

Example:

// Send multiple messages to the endpoint
{ "message": "Message 1" }
{ "message": "Message 2" }
{ "message": "Message 3" }

Testing WebSocket Functionality with Assertions

Similar to HTTP requests, you can use assertions to validate the responses and behavior of your WebSocket endpoints.

  1. Assertions in Event Handlers:

    • Within your event handlers (especially the “Message” event), you can add assertions to validate the received data.
    • Postman provides a variety of assertion libraries, including pm.expect(), which can be used for comparisons, string matching, and more.

  2. Assertions for Event Triggers:

    • You can even assert on when specific WebSocket events are triggered. For example, you can check that the “Close” event is triggered when the server closes the connection.

Example:

// Asserting the received message content
pm.test("Verify message content", function () {
  var message = pm.response.text();
  pm.expect(message).to.equal("Hello from WebSocket!");
});


//  Asserting the Close event triggered
pm.test("Check for Close event", function () {
  pm.expect(pm.event.name).to.equal("close");
});

Practical WebSocket Testing Scenarios

Here are some practical scenarios for using WebSockets in Postman for API testing:

  • Real-time chat app: Send and receive messages, verify user presence, and test for message delivery.
  • Stock market data streaming: Subscribe to data feeds, receive real-time updates, and perform data analysis.
  • Live location tracking: Send location updates from devices, receive location data, and test accuracy and latency.
  • Gamification features: Test real-time gameplay interactions, player updates, and score synchronization.

Conclusion

Postman provides a powerful and versatile platform for testing WebSocket endpoints. By leveraging its features for sending messages, handling events, and implementing assertions, you can thoroughly validate the functionality and performance of your real-time applications. This guide provides a solid foundation for effectively incorporating WebSocket testing into your API testing workflow.

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