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Bug Report: ack Callback from Client not Received in NestJS @SubscribeMessage Handler
Is there an existing issue for this?
- [x] I have searched the existing issues
Current behavior
When emitting a Socket.IO event with a callback from the client (i.e., emit(event, payload, ack)), the third parameter ack is not received in the NestJS gateway method decorated with @SubscribeMessage. Only two arguments are passed: the socket instance and the payload.
Minimum reproduction code
https://github.com/duc190604/bug_report
Steps to reproduce
How to Run and Test the Application 🔧 Start the Server (NestJS): Open terminal.
Navigate to the server directory.
Run the server with the appropriate command (e.g., npm run start:dev).
The server will be running at: http://localhost:3001/
💻 Start the Client (React): Open a new terminal.
Navigate to the client directory.
Run the client with the appropriate command (e.g., npm start).
The client will be running at: http://localhost:3000/
🌐 Test WebSocket Connection
- Open the client in a browser: Go to: http://localhost:3000/
You should see a UI with:
Connection status (🟢 Connected or 🔴 Disconnected)
An input field for typing messages
A "Send" button
- Test message sending: Type a message (e.g., Hello Server) in the input box
Press Enter or click the Send button
Wait for the server response displayed below the input
🧾 Check Client Logs (Browser Console): Open DevTools (press F12)
Watch for the following logs:
"Connected to server" when the connection is established
"Sending message: ..." when a message is sent
"Received acknowledgment: ..." when the server responds
🖥️ Check Server Logs (Terminal): In the terminal running the server, observe:
"Server is running on port 3001" after the server starts
"args: ..." when a message is received from the client ( and don't include ack)
Expected behavior
The ack callback function should be passed to the last parameter of the handler, and be callable from within NestJS so the server can send an acknowledgment to the client.
Package
- [ ] I don't know. Or some 3rd-party package
- [ ]
@nestjs/common - [ ]
@nestjs/core - [ ]
@nestjs/microservices - [ ]
@nestjs/platform-express - [ ]
@nestjs/platform-fastify - [x]
@nestjs/platform-socket.io - [x]
@nestjs/platform-ws - [ ]
@nestjs/testing - [x]
@nestjs/websockets - [ ] Other (see below)
Other package
No response
NestJS version
11.1.3
Packages versions
platform-socket.io version : 11.1.3
platform-express version : 11.1.3
websockets version : 11.1.3
schematics version : 11.0.5
mongoose version : 11.0.3
passport version : 11.0.5
swagger version : 11.2.0
testing version : 11.1.1
common version : 11.1.3
config version : 4.0.2
core version : 11.1.3
jwt version : 11.0.0
cli version : 11.0.7
Node.js version
v22.13.0
In which operating systems have you tested?
- [ ] macOS
- [x] Windows
- [ ] Linux
Other
No response
it looks like your repository https://github.com/duc190604/ChatApp_BE-NestJS is not public
I’ve only included a placeholder link for now as I don’t have time to prepare a full reproduction. Please refer to the description above for a clear explanation of the issue.
Please provide a minimum reproduction repository. You can start one by running npm init nest in your terminal
why reproductions are required
Have you tried this https://github.com/nestjs/nest/issues/581#issuecomment-389267854
Have you tried this #581 (comment)
Running the PR locally works well, and one is able to get the acknowledgement.
