Send message to client any moment Netty Io

Question

I have an architecture based on micro services, netty io runs on a spring boot application, when I want to send a message to a client I have to wait for a message from the client to send the reply to the one I want to send. How could I send a message to the client without waiting for him to communicate with me? I'm lost in this step.

Answer 1

You can process like that :

1. Let the client connect on your server
2. Let the client send a Hello Message (to be sure is one of your client)
3. Catch the message on the server and store a reference on the channel (which is available on each channel handler by calling ctx.channel() )
4. Catch channelInactive event to remove the reference when the client disconnects

Instead of waiting for a HelloMessage, you can also catch the channelActive event but it is fired each time somebody connects to your listened port, even if is not one of your client. That's why I prefer using an "Hello Message"

Now, you have a reference on the channel and you can send a message when you want by calling channel.writeAndFlush()