Handling multiple clients at the same time

afkuser

Is there any way to accept several clients at the same time and receive data from them at the same time?
Example:
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In this example I won't be able to accept multiple clients but I will be able to accept one client and I will be able to read the sent client data

Example 2:
If I remove "task:wait()" on line 30, I can receive multiple clients but I can't read their sent data

Samir

You must stock the result of the accept() Task in a table, that will contains all the clients Socket instances like this, and don't forget to sleep() :

local clients = { }

while true do
    server:accept().after = function (socket)
         clients[#clients+1]  = socket
   end
   sleep()
end

afkuser

Thanks

local net = require('net')

local BIND_IP = '127.0.0.1'
local BIND_PORT = 25565

local server = net.Socket(BIND_IP, BIND_PORT)

server.blocking = false
assert(server:bind(), net.error)

local clients = {}

local function handle(socket)
    local obj = socket.obj

    local function clean()
        for i, s in pairs(clients) do
            if s.obj == obj then
                socket[i] = nil
                print('r')
            end
        end
    end

    while not socket.dead do
        obj:recv().after = function(data)
            if not data then
                socket.dead = true

                return
            end

            print(data)
        end

        sleep()
    end

    clean()
end

async(function()
    while true do
        for _, socket in pairs(clients) do
            if not socket.handled then
                socket.handled = true

                async(handle, socket)
            end
        end

        sleep()
    end
end)

while true do
    local task = server:accept()

    function task.after(socket)
        clients[#clients + 1] = {
            obj = socket,
            handled = false,
        }
    end

    sleep()
end

steve64

I tried this approach and it works, but the message exchange is very slow if each client sends data and waits for a reply from the server instead of just letting the server printing the data received.
Is it due to task/coroutine switching?
Using a similar solution in Python with a multi-threaded server is lot faster...
What's the faster approach to have a LuaRT server accepting simultaneous clients?

Samir

How many clients do you have ?
I don't think Task switch is so Time consuming

I have not tested scenarios with a lots of Tasks/clients.

May be you should use net.select()

Edit: I have looked more deeply at the code you posted I think something is wrong with the way you use async Sockets. I will dig into it.

steve64

The code was posted by afkuser. I started from that adding server replies and client's wait for reply.
Without a send-reply scheme, the transmission is fast since probably the clients have just to fill a buffer and go on.
But if you add replay/ack the speed is unacceptable.

I actually liked the usage of tasks in LuaRT and hoped that they were competitive w.r.t. Python multi-threading...

By the way, I just retried an example based on net.select() instead and it looks as I'm able to manage interleaved accept and message receive/reply in the server with good performance on latest LuaRT 1.8.x with 10 or more clients and hundreds of messages by each of them.
It's not clear to me why the task/async approach was so slow, but at least I have a solution with select that I can experiment in my applications.

Samir

LuaRT Tasks are a thin layer around Lua coroutines, so they cannot outperform python multithreading.

I will investigate this slow Socket behaviour with Tasks, but can you post code that can reproduce this, to be sure it's not a async misuse ?