Lua Socket cannot be properly stopped by Ctrl+C

Question

I have a standalone lua script that uses lua sockets to connect to a server via TCP IP. It uses receive call to receive data from that server. It works, however, when I try to stop it with Ctrl+C, one of the two scenarios is happening:

-If there is currently no traffic and receive is waiting, Ctrl+C will have no effect. The program will continue to run, and will have to be terminated by kill.

-If there is traffic, the program will exit with the below printout and with the socket still open and with the server not accepting another connection:

lua: luaSocketTest.lua:15: interrupted!
stack traceback:
[C]: in function 'receive'
luaSocketTest.lua:15: in function 'doWork'
luaSocketTest.lua:22: in main chunk
[C]: ?

I tried using pcall to solve the second scenario, without success. pcall doesn't return, the process still throws the error.

Sample of my program is below:

local socket = require ("socket")
local ip = "localhost"
local port = 5003

function doWork ()
    print ("Starting socket: "..ip..":"..port)
    client = assert(socket.connect(ip, port))
    print ("Socket Accepted")
    client:send("TEST TEST")
    while 1 do
      local byte, err = client:receive (1)
      if not err then
         print (byte)
      end
    end
end
while 1 do
  local status = pcall(doWork())
  print ("EXITED PCALL WITH STATUS: "..tostring(status))
  if not status then client:close() end
end

I think this can be avoided by setting the client timeout to 0, and periodically checking back for new data arrived at the socket. During the sleep, it should be possible to use ctrl-c. — jpjacobs, Oct 03 '13 at 09:11

score 2 · Answer 1 · answered Nov 05 '13 at 22:40

This would be quite a change, but you could employ lua-ev. It allows to add Signal handlers, which is exactly what is required to react to ctrl-c.

local socket = require'socket'
-- make connect and send in blocking mode
local client = socket.connect(ip,port)
client:send('TEST TEST')

-- make client non-blocking
client:settimeout(0)
ev.IO.new(function()
  repeat
    local data,err,part = client:receive(10000) 
    print('received',data or part)
  until err
end,client:getfd(),ev.READ):start(ev.Loop.default)

local ev = require'ev'
local SIGINT = 2

ev.Signal.new(function()
  print('SIGINT received')
end,SIGINT):start(ev.Loop.default)

ev.Loop.default:loop()

Lua Socket cannot be properly stopped by Ctrl+C

1 Answers1