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Migrating Ajax web application to web socket

I think I'm just missing a little detail that is preventing me from seeing the whole picture.

I have a web application which use ajax request every x time to update client with new information or tasks.

I also have a long running process on the server which is a java computation engine. I would like this engine to send update to the client.

  1. I am wondering how to migrate my web app to using websocket. Probably phpwebsocket or similar. Can my server 'decide' to send information to a specific client? It seems possible looking at the php-websocket.

  2. Can my java backend long process use the websocket server to send notification to a specific client. How? well I can say that my java app could use a class that could send over websocket instead of http.

But how the websocket server knows to which client to send the 'info'. I am puzzle by all this. Any document that explain this in more details? It seems that the websocket could create an instance of my web application.

Thanks

Solution

  • Your server, which will have an arbitrary number of active client sockets, decides which ones to write to (possibly in response to input from the user).

    phpwebsocket (which is still very rough around the edges) has a User class with $id, $socket (this is the underlying TCP socket), and $handshake fields. You could extend that class with additional metadata about the User (e.g. a computation identifier). Or you could use an array mapping from computation id to User.

    Perhaps when Java computation n finishes, you can look up the socket associated with that computation, and write to its socket.