Implementing a re-connecting socket

[Jörg Krause]

Hi,

I am trying to implement a client which tries to reconnect to server if, for whatever reason, is not available sometimes. My application is about piping the stdout of arecord to a TCP socket on a server. The application works fine, but is not bullet-proof if the server is not ready or is restarted. I want the client to reconnect to the server, without the need of a process monitor on the client side.

I found a similar nodejs example: https://gist.github.com/sio2boss/6334089

local spawn = require('childprocess').spawn

local net = require('net')

local args = {

  "-M",

  "-D", "hw:0,1",

  "-t", "raw",

  "-c", "2",

  "-r", "48000",

  "-f", "S16_LE",

}

local sock

sock = net.Socket:new()

local function doConnect()

  print("Connecting...")

  sock:connect(1234, '192.168.1.157')

end

local function onConnect()

  print("Connected")

  local arecord

  arecord = spawn("arecord", args)

  arecord:on("error", function(err)

    print("Spawn error:", err)

  end)

  arecord:on("exit", function(exit_status)

    print("Exit with " .. exit_status)

  end)

  arecord.stdout:pipe(sock)

  arecord.stderr:pipe(sock)

end

local function onError(err)

  print("Socket error:", err)

  if err == 'ECONNREFUSED' then

    sock:setTimeout(1000, doConnect)

  elseif err == 'EPIPE' then        

    sock:setTimeout(1000, doConnect)   

  end                               

end  

   

sock:on("connect", onConnect)

sock:on("error", onError)    

                         

doConnect()

The client tries one time to reconnect, but not more:

# luvit client.lua 

Connecting...

Socket error: ECONNREFUSED

Connecting...

# 

Any idea what is wrong with my code?

Best regards,

Jörg Krause

[Ryan Phillips]

Hey Jörg,

In your doConnect function you will want to instantiate a new socket there. You can't reuse the same socket instance.

Regards,

Ryan

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[Jörg Krause]

Hey Ryan,

On Sunday, January 29, 2017 at 8:04:42 PM UTC+1, Ryan Phillips wrote:

Hey Jörg,

In your doConnect function you will want to instantiate a new socket there. You can't reuse the same socket instance.

I changed my client implementation and it seems to work now:

local fs = require('fs')

local spawn = require('childprocess').spawn

local net = require('net')

local args = {

  "-M",

  "-D", "record_left",

  "-t", "raw",

  "-c", "1",

  "-r", "48000",

  "-f", "S16_LE",

}

local function doConnect()

  local arecord

  local sock

  local ip = "192.168.0.101"

  local port = 1234

  if not ip or not port then return end

  print(string.format("Connecting to %s:%s", ip, port))

  sock = net.createConnection(port, string.format("%s", ip))

  sock:on("connect", function (err)

    if err then print("Connection error:", err) end

    print("Connected")

    arecord = spawn("arecord", args)

    arecord:on("error", function(err)

      print("Spawn error:", err)

    end)

    arecord:on("exit", function(exit_status)

      print("Exit with " .. exit_status)

      sock:setTimeout(1000, doConnect)

    end)

    arecord.stdout:on('data', function(data)

      sock:write(data)

    end)

    arecord.stderr:pipe(process.stderr)

  end)

  sock:on("error", function(err)

    if err then

      print("Socket error:", err)

      if arecord then

        arecord:kill('sigkill')

      else

        sock:setTimeout(1000, doConnect)

      end

    end

  end)

end

doConnect()

However, I am not sure if it is done correct. Maybe this implementation still has some flaws?

 

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[Ryan Phillips]

That certainly looks like it should work.

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