How to send different notifications to different users using socket.io

Question

I'm new to socket.io and have caught up with the basic connections. But I would like to know how to send different notifications to different users. For example there are users 1 to 4 and category A to D. Each user might be subscribed to different catergories. See the table below

USER   | CATEGORY
1      | A
2      | A
4      | A
2      | B
4      | B
1      | C
2      | C
3      | C
4      | C
3      | D
4      | D

So if any new posts are added to any category, all the subscribed users should get respective notification. I know this may sounds silly, but I'm really confused that whether I need to create rooms with category ID and how to join all subscribed users to that rooms and so.

Any helps would be greatful. Thanks.

You have to filter out socker which belongs to user need to be notified. Same question ask in here as well https://stackoverflow.com/questions/26297373/send-update-notification-to-particular-users-using-socket-io — kamprasad, Nov 06 '19 at 09:29

score 0 · Answer 1 · answered Nov 07 '19 at 13:26

If you wish to avoid using individual rooms you can just keep track of the connections yourself. You can do something like this

var clients = [];
io.sockets.on('connection', function(socket) {
   clients.push({     //Store information on the client when they connect
      id: socket.id,
      conn: socket,
      category: []
   });
   socket.on('disconnect', function() {
      clients = clients.filter(client => client.id != socket.id);  //Remove the disconnecting client
   });
});

Then once you have that setup whenever you want to update a category you can do this:

function updateCat(categoryName, updateData){
   clients.forEach(client => {
      if(client.category.includes(categoryName)){   //Check if the client is subscribed
         client.conn.emit('category_update', updateData);
      }
   });
}

This is a possible solution over using rooms, if you have any questions lemme know.

How to send different notifications to different users using socket.io

1 Answers1