Lua self method call attempt (a nil value) - lua

Question

I wrote a small class to receive data over TCP, but periodically (not constantly, sometimes the script runs long enough and receives data) I get an error:
.\modules\tcp.lua:83: attempt to call method '_parsing' (a nil value)
I can't figure out why the object loses the method that it had in the self and which worked. When creating the class I am using the module https://github.com/kikito/middleclass
After creating an object, I call in while loop:
feed:receive()
Class sample
os.setlocale("C")
package.path = package.path .. ";./libs/?.lua";
package.path = package.path .. ";./libs/luasocket/lua/?.lua";
package.cpath = package.cpath .. ";./libs/luasocket/?.dll";
package.cpath = package.cpath .. ";./libs/luasocket/mime/?.dll";
package.cpath = package.cpath .. ";./libs/luasocket/socket/?.dll";
local class = require "middleclass";
local socket = require "socket";
local struct = require "struct";
local msgpack = require "msgpack";
local type = type
local table = table
local string = string
local TCP = class("TCP")
function TCP:initialize(address, port, logger, onOpen, onClose, onMessages)
self.address = address
self.port = port
self.logger = logger
self.onOpen = onOpen
self.onClose = onClose
self.onMessages = onMessages
self.socket = nil
self.connected = false
self.seq_in = 0
self.chunk_in = ""
self.seq_out = 0
self.chunk_out = ""
end
function TCP:_connection_made()
if not self.socket then
self.socket = socket.tcp()
local status, _ = self.socket:connect(self.address, self.port)
if status then
self.socket:setoption("reuseaddr", true)
self.socket:setoption("tcp-nodelay", true)
self.socket:setoption("keepalive", true)
self.socket:settimeout(0)
self.logger:info("Connection open "..self.address..":"..self.port.."")
self.connected = true
if self.onOpen then
self.onOpen()
end
else
self.socket = nil
end
end
end
function TCP:_connection_close()
self.logger:info("Connection close "..self.address..":"..self.port.."")
self.socket = nil
self.connected = false
self.seq_in = 0
self.chunk_in = ""
self.seq_out = 0
self.chunk_out = ""
if self.onClose then
self.onClose()
end
end
function TCP:_receive()
local data, error, partial = self.socket:receive("*a")
if (not data) and (error ~= "timeout") then
self.logger:error("Connection error "..error)
self:_connection_close()
return nil, error
end
data = data or partial
if not data then
return nil, error
else
return self:_parsing(data)
end
end;
function TCP:_parsing(data)
local messages = {}
if self.chunk_in ~= "" then
data = self.chunk_in..data
self.chunk_in = ""
end
while string.len(data) ~= 0 do
if string.len(data) >= 10 then
local size, seq = struct.unpack("<HL", data)
if string.len(data) >= size + 10 then
if seq ~= self.seq_in + 1 then
self.logger:warn("Connection expected seq: "..(self.seq_in + 1)..", received seq: "..seq)
end
self.seq_in = seq
local msg = msgpack.unpack(string.sub(data, 11, 10 + size))
data = string.sub(data, 11 + size)
table.insert(messages, msg)
else
self.chunk_in = self.chunk_in..data
data = ""
end
else
self.chunk_in = self.chunk_in..data
data = ""
end
end
if self.onMessages then
self.onMessages(messages)
else
return messages, ""
end
end;
function TCP:_send(msg)
self.logger:debug("Try to send message", msg)
if type(msg) == "table" then
local data = msgpack.pack(msg)
self.seq_out = self.seq_out + 1
local frame = struct.pack("<HL", string.len(data), self.seq_out)
local index, error = self.socket:send(frame..data)
if error then
self.logger:error("Connection send error "..error)
if error == "closed" then
self:_connection_close()
end
end
end
end
function TCP:open()
if not self.connected then
self:_connection_made()
end
end
function TCP:close()
if self.connected then
self:_connection_close()
end
end
function TCP:receive()
if not self.connected then
self:_connection_made()
else
return self:_receive()
end
end
function TCP:send(msg)
if not self.connected then
return nil
else
return self:_send(msg)
end
end
return TCP