Real-time forum information push

I would like to ask if you want to implement real-time message push for a webpage forum. the frontend and backend are separated and use node as the middle layer. I plan to use socket on the client and node. io establishes a persistent connection, while the node does not need to maintain a persistent connection with the backend. the node provides interfaces and calls the connection when the backend has a message... I would like to ask if you want to implement real-time message push for a webpage forum. the frontend and backend are separated and use node as the middle layer. I plan to use socket on the client and node. i/O establishes a persistent connection, while the node does not need to maintain a persistent connection with the backend. the node provides an interface, and calls the interface when there is a message at the backend to tell the node end who will deliver the message. How can I determine whether the client is online or whether a persistent connection has been established with node? If the corresponding user is found based on the information provided by the backend, such as the user ID, for message transmission?