Please update documentation to show how to reject a packet from socket middleware

Open Beginner friendly
#3,876 1 comment 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
65/100
Issue type
Documentation
Clarity
Mostly clear
Activity status
Quiet
Tech stack
express, javascript, nodejs
Domain
backend, documentation

Research direction

Start with the linked Socket.IO v3 socket middleware section and compare its existing guidance with the provided middleware example. Update the documentation with a concise packet-rejection example and explain the expected dropped-packet behavior; done when the section clearly covers this requested use case.

Written by the indexing model from the issue text.

Description

documentation

Is your feature request related to a problem? Please describe.
I spent about an hour messing around to figure this out, but I needed a way to drop (or reject) a packet from a middleware, without erroring out (next(error)). This is for an ACL I'm working on to only allow users to emit on a channel if they have permission.
I have found a solution, and feel it should be included in the documentation for future reference.

Describe the solution you'd like
I would like, probably in the socket middleware section, to show a way to drop packets from a middleware (I have found a way, but any way really).

I did it by simply returning from the middleware:

io.use(function(socket,next) {
    socket.use(function([event,data],next) {
        if(true /* some condition for dropping the packet */) return
        else next()
    })
    next()
})

Describe alternatives you've considered
I've only really tried the above solution I found (other than about an hour of googling and eating the docs)

Additional context
As in my context, this functionality is very useful for user/access control, and allowed me to consolidate a good amount of code into this one middleware. This functionality is also already present, but not mentioned in the documentation and examples, and I believe this functionality could prove very popular if the documentation could mention it and have the idea in developers minds

Also, here is a fully functional example (using express and socket.io) demonstrating dropping every other packet based on a incrementing id:


const app = require('express')()

const http = require('http').Server(app)

const io = require('socket.io')(http)

io.use(function(socket,next) {
	console.log("io middleware hit")
	socket.use(function([event,data],next) {
		console.log("socket middleware hit")
		if(data.ttl % 2) {
			console.log("dropping packet: ",data.ttl)
			return
		} else {
			console.log("passing packet: ",data.ttl)
			next()
		}
	})
	next()
})
io.on("connection",function(socket) {
	socket.on("ping",function(data,ack) {
		console.log("server got client ping: ",data.ttl)
		ack(data)
		socket.emit("pong",data,function(res) {
			console.log("client acknowledged pong: ",res.ttl)
		})
	})
})
io.on("ping",function(data,ack) {
	console.log("server broadcast got ping: ",data.ttl)
	ack(data)
	socket.emit("pong",data)
})

app.get("/",(req,res) => {
	res.send(`
<!DOCTYPE html>
<html>
    <head>
        <title>Test</title>
    </head>
    <body>
        <script src="/socket.io/socket.io.js"></script>
        <script>
            var socket = io();
            var pid = 0
            var int
            //console.log("awaiting socket connection")
            socket.on('connect',function() {
                console.log("socket connected")
                int = setInterval(function() {
                    let _pid = pid++
                    console.log("client pinging server: ",_pid)
                    socket.emit("ping",{ttl: _pid},function(res) {
                        console.log("Server acknowledged ping: ",res.ttl)
                    })
                },1000)
            })
            socket.on('disconnect',function() {
                console.log("socket disconnected")
                clearInterval(int)
            })
            socket.on('pong',function(data,ack) {
                console.log("client got pong: ",data.ttl)
                ack(data)
            })
        </script>
    </body>
</html>
		`)
})

http.listen(8000,() => {
	console.log("listening on http://localhost:8000/")
})

Running this example shows that all packets where ttl is odd are dropped, and no ack function is called and no error is emitted.

I have not gone much into depth on this though (I got the functionality I needed), but I'm sure adding it to the documentation and having other devs look at it will uncover more features and edge cases.

Thank you for considering my request!

Dominant language
TypeScript
Stars
63.2k
Forks
10.3k
Avg merge
11d 20h
Merged PRs (30d)
2

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from socketio/socket.io

All issues in socketio/socket.io

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.