Socket.io: How to limit the size of emitted data from client to the websocket server

Question

I have a node.js server with socket.io. My clients use socket.io to connect to the node.js server.

Data is transmitted from clients to server in the following way:

Answer 1

So the easiest thing to do is just check the size of the data before doing anything with it.

socket.on('someevent', function (data) {
    if (JSON.stringify(data).length > 10000) //roughly 10 bytes
        return;

    console.log('valid data: ' + data);
});

To be honest, this is a little inefficient. Your client sends the message, socket.io parses the message into an object, and then you get the event and turn it back into a String.

If you want to be even more efficient then on the client side you should be enforcing max lengths of messages.

For even more efficiency (and to protect against malicious users), as packets come into Socket.io, if the length gets too long, then you should discard them. You'll either need to figure a way to extend the prototypes to do what you want or you'll need to pull the source and modify it yourself. Also, I haven't looked into the socket.io protocol but I'm sure you'll have to do more than just "discard" the packet. Also, some packets are ack-backs and nack-backs so you don't want to mess with those, either.

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Side note: If you ONLY care about the number of keys then you can use Object.keys(obj) which returns an array of keys:

if (Object.keys(obj).length > 10)
    return;