Build a Chat App: Lambda, WebSocket, and API Gateway (Node.js)

Table of Contents

1. Introduction
2. Setting up the WebSocket in API Gateway
   • Route selection expression
   • Predefined routes
   • Custom routes
   • Lambda function integration
   • Creating the Lambda function
3. Connecting to the WebSocket from the client-side
   • Initiating the connection
   • Event listeners for connection status
   • Sending events to the WebSocket
   • Handling received events
4. Implementing functionality for the chat application
   • Updating user list
   • Sending public messages
   • Sending private messages
   • System messages and notifications
   • Disconnecting from the chat

Implementing a Real-Time Chat Application Using Websockets in AWS Lambda and API Gateway

In this tutorial, we will learn how to Create a real-time chat application using websockets powered by AWS Lambda and API Gateway. The application will allow users to connect, send public and private messages, and receive live updates in real-time. We will start by setting up the WebSocket in API Gateway and creating the Lambda function to handle the events. Then, we will connect to the WebSocket from the client-side and implement the functionality for the chat application.

1. Introduction

Real-time communication is essential in today's digital world, and websockets provide a reliable and efficient way to enable it. By using AWS Lambda and API Gateway, we can easily create a serverless chat application that allows users to connect and exchange messages in real-time.

2. Setting up the WebSocket in API Gateway

To begin, we will set up the WebSocket in API Gateway, which will handle the connections and route the events to our Lambda function.

Route selection expression

We will define a route selection expression to determine how the WebSocket events will be routed. We can use the request by action as the expression.

Predefined routes

API Gateway provides several predefined routes for WebSocket events, such as connect, disconnect, and default. These routes will be triggered Based on the corresponding events from the WebSocket clients.

Custom routes

In addition to the predefined routes, we can define our own custom routes that our Lambda function will handle. For example, we can define routes for setting a username, sending public messages, and sending private messages.

Lambda function integration

We will integrate our Lambda function with the routes defined in API Gateway. Each route will be associated with the Lambda function to handle the corresponding WebSocket events.

Creating the Lambda function

Next, we will create the Lambda function that will power our WebSocket. We will write the code to handle the events received from the WebSocket clients. The events will contain useful information such as the connection ID and the route key, which we can use to route the events to the appropriate handlers.

3. Connecting to the WebSocket from the client-side

Now that our WebSocket is set up in API Gateway, we can connect to it from the client-side and start exchanging messages in real-time.

Initiating the connection

Using the WebSocket API available in all modern browsers, we will initiate a connection to our WebSocket by providing the WebSocket URL. Once the connection is established, we will receive an event indicating the connection status.

Event listeners for connection status

We will add event listeners to handle the WebSocket connection status. When the connection is opened, we will update the UI to indicate that the connection is established. Similarly, when the connection is closed, we will update the UI to indicate that the connection is closed.

Sending events to the WebSocket

To send messages to the WebSocket, we will create callback functions that will be called when the user interacts with the chat application. For example, when the user sends a public or private message, we will send the corresponding event to the WebSocket.

Handling received events

When we receive events from the WebSocket, we will parse the data and update the UI accordingly. We will handle events such as receiving a list of users, a public message, a private message, or a system message. The UI will be updated in real-time as new events are received.

4. Implementing functionality for the chat application

In this section, we will implement the functionality for the chat application using the WebSocket.

Updating user list

When we receive a list of users from the WebSocket, we will update the user list in the UI. We will display the usernames of the connected users in real-time.

Sending public messages

Users will be able to send public messages that will be delivered to all connected users. We will send the public message to the WebSocket, which will distribute it to all the clients. The UI will display the public messages in real-time.

Sending private messages

Users will also be able to send private messages to specific recipients. We will send the private message to the WebSocket, specifying the recipient and the content of the message. The WebSocket will deliver the private message only to the intended recipient. The UI will display the private messages in real-time.

System messages and notifications

The WebSocket will also send system messages and notifications to the clients. For example, when a user joins or leaves the chat, a system message will be sent to notify all the users. The UI will display these system messages and notifications in real-time.

Disconnecting from the chat

Users will have the option to disconnect from the chat. When a user disconnects, the WebSocket will notify the other users, and the UI will be updated to reflect the changes in the user list.

By following this tutorial, You will be able to create a real-time chat application using websockets in AWS Lambda and API Gateway. The application will provide a seamless and interactive chat experience for users, allowing them to connect, exchange messages, and receive live updates in real-time.

Highlights:

• Setting up the WebSocket in API Gateway
• Connecting to the WebSocket from the client-side
• Implementing functionality for the chat application
• Real-time updates and seamless communication

FAQ:

Q: Can I use a different storage method instead of an object to save user information? A: Yes, you can use other storage methods such as a MySQL database or any preferred method. Using an object for demonstration purposes simplifies the example.

Q: Is it possible to have multiple users connected to the chat application at the same time? A: Yes, multiple users can connect to the chat application simultaneously. The chat application will handle and deliver messages among connected users in real-time.

Q: Can private messages be sent to multiple recipients? A: No, private messages are meant to be sent to a specific recipient. To send a message to multiple recipients, you can use the public message functionality.

Q: How secure is the communication in the chat application? A: The communication in the chat application is secured and encrypted by default when using websockets in AWS Lambda and API Gateway. Additionally, you can implement additional security measures, such as authentication and authorization, to ensure a secure chat environment.