File

-- 
-- server.lua by blastbeat of the luadch project
-- Re-used here under the MIT/X Consortium License
-- 
-- Modifications (C) 2008-2010 Matthew Wild, Waqas Hussain
--

-- // wrapping luadch stuff // --

local use = function( what )
	return _G[ what ]
end
local clean = function( tbl )
	for i, k in pairs( tbl ) do
		tbl[ i ] = nil
	end
end

local log, table_concat = require ("util.logger").init("socket"), table.concat;
local out_put = function (...) return log("debug", table_concat{...}); end
local out_error = function (...) return log("warn", table_concat{...}); end

----------------------------------// DECLARATION //--

--// constants //--

local STAT_UNIT = 1 -- byte

--// lua functions //--

local type = use "type"
local pairs = use "pairs"
local ipairs = use "ipairs"
local tonumber = use "tonumber"
local tostring = use "tostring"

--// lua libs //--

local os = use "os"
local table = use "table"
local string = use "string"
local coroutine = use "coroutine"

--// lua lib methods //--

local os_difftime = os.difftime
local math_min = math.min
local math_huge = math.huge
local table_concat = table.concat
local string_len = string.len
local string_sub = string.sub
local coroutine_wrap = coroutine.wrap
local coroutine_yield = coroutine.yield

--// extern libs //--

local luasec = use "ssl"
local luasocket = use "socket" or require "socket"
local luasocket_gettime = luasocket.gettime

--// extern lib methods //--

local ssl_wrap = ( luasec and luasec.wrap )
local socket_bind = luasocket.bind
local socket_sleep = luasocket.sleep
local socket_select = luasocket.select

--// functions //--

local id
local loop
local stats
local idfalse
local closeall
local addsocket
local addserver
local getserver
local wrapserver
local getsettings
local closesocket
local removesocket
local removeserver
local wrapconnection
local changesettings

--// tables //--

local _server
local _readlist
local _timerlist
local _sendlist
local _socketlist
local _closelist
local _readtimes
local _writetimes

--// simple data types //--

local _
local _readlistlen
local _sendlistlen
local _timerlistlen

local _sendtraffic
local _readtraffic

local _selecttimeout
local _sleeptime

local _starttime
local _currenttime

local _maxsendlen
local _maxreadlen

local _checkinterval
local _sendtimeout
local _readtimeout

local _cleanqueue

local _timer

local _maxclientsperserver

local _maxsslhandshake

----------------------------------// DEFINITION //--

_server = { } -- key = port, value = table; list of listening servers
_readlist = { } -- array with sockets to read from
_sendlist = { } -- arrary with sockets to write to
_timerlist = { } -- array of timer functions
_socketlist = { } -- key = socket, value = wrapped socket (handlers)
_readtimes = { } -- key = handler, value = timestamp of last data reading
_writetimes = { } -- key = handler, value = timestamp of last data writing/sending
_closelist = { } -- handlers to close

_readlistlen = 0 -- length of readlist
_sendlistlen = 0 -- length of sendlist
_timerlistlen = 0 -- lenght of timerlist

_sendtraffic = 0 -- some stats
_readtraffic = 0

_selecttimeout = 1 -- timeout of socket.select
_sleeptime = 0 -- time to wait at the end of every loop

_maxsendlen = 51000 * 1024 -- max len of send buffer
_maxreadlen = 25000 * 1024 -- max len of read buffer

_checkinterval = 1200000 -- interval in secs to check idle clients
_sendtimeout = 60000 -- allowed send idle time in secs
_readtimeout = 6 * 60 * 60 -- allowed read idle time in secs

_cleanqueue = false -- clean bufferqueue after using

_maxclientsperserver = 1000

_maxsslhandshake = 30 -- max handshake round-trips

----------------------------------// PRIVATE //--

wrapserver = function( listeners, socket, ip, serverport, pattern, sslctx, maxconnections ) -- this function wraps a server

	maxconnections = maxconnections or _maxclientsperserver

	local connections = 0

	local dispatch, disconnect = listeners.onconnect, listeners.ondisconnect

	local accept = socket.accept

	--// public methods of the object //--

	local handler = { }

	handler.shutdown = function( ) end

	handler.ssl = function( )
		return sslctx ~= nil
	end
	handler.sslctx = function( )
		return sslctx
	end
	handler.remove = function( )
		connections = connections - 1
		if handler then
			handler.resume( )
		end
	end
	handler.close = function()
		socket:close( )
		_sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
		_readlistlen = removesocket( _readlist, socket, _readlistlen )
		_server[ip..":"..serverport] = nil;
		_socketlist[ socket ] = nil
		handler = nil
		socket = nil
		--mem_free( )
		out_put "server.lua: closed server handler and removed sockets from list"
	end
	handler.pause = function()
		if not handler.paused then
			socket:close( )
			_sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
			_readlistlen = removesocket( _readlist, socket, _readlistlen )
			_socketlist[ socket ] = nil
			socket = nil;
			handler.paused = true;
		end
	end
	handler.resume = function()
		if handler.paused then
			socket = socket_bind( ip, serverport );
			socket:settimeout( 0 )
			_readlistlen = addsocket(_readlist, socket, _readlistlen)
			_socketlist[ socket ] = handler
			handler.paused = false;
		end
	end
	handler.ip = function( )
		return ip
	end
	handler.serverport = function( )
		return serverport
	end
	handler.socket = function( )
		return socket
	end
	handler.readbuffer = function( )
		if connections > maxconnections then
			handler.pause( )
			out_put( "server.lua: refused new client connection: server full" )
			return false
		end
		local client, err = accept( socket )	-- try to accept
		if client then
			local ip, clientport = client:getpeername( )
			client:settimeout( 0 )
			local handler, client, err = wrapconnection( handler, listeners, client, ip, serverport, clientport, pattern, sslctx ) -- wrap new client socket
			if err then -- error while wrapping ssl socket
				return false
			end
			connections = connections + 1
			out_put( "server.lua: accepted new client connection from ", tostring(ip), ":", tostring(clientport), " to ", tostring(serverport))
			if dispatch then
				return dispatch( handler );
			end
			return;
		elseif err then -- maybe timeout or something else
			out_put( "server.lua: error with new client connection: ", tostring(err) )
			return false
		end
	end
	return handler
end

wrapconnection = function( server, listeners, socket, ip, serverport, clientport, pattern, sslctx ) -- this function wraps a client to a handler object

	socket:settimeout( 0 )

	--// local import of socket methods //--

	local send
	local receive
	local shutdown

	--// private closures of the object //--

	local ssl

	local dispatch = listeners.onincoming
	local status = listeners.onstatus
	local disconnect = listeners.ondisconnect
	local drain = listeners.ondrain

	local bufferqueue = { } -- buffer array
	local bufferqueuelen = 0	-- end of buffer array

	local toclose
	local fatalerror
	local needtls

	local bufferlen = 0

	local noread = false
	local nosend = false

	local sendtraffic, readtraffic = 0, 0

	local maxsendlen = _maxsendlen
	local maxreadlen = _maxreadlen

	--// public methods of the object //--

	local handler = bufferqueue -- saves a table ^_^

	handler.dispatch = function( )
		return dispatch
	end
	handler.disconnect = function( )
		return disconnect
	end
	handler.setlistener = function( self, listeners )
		dispatch = listeners.onincoming
		disconnect = listeners.ondisconnect
		status = listeners.onstatus
		drain = listeners.ondrain
	end
	handler.getstats = function( )
		return readtraffic, sendtraffic
	end
	handler.ssl = function( )
		return ssl
	end
	handler.sslctx = function ( )
		return sslctx
	end
	handler.send = function( _, data, i, j )
		return send( socket, data, i, j )
	end
	handler.receive = function( pattern, prefix )
		return receive( socket, pattern, prefix )
	end
	handler.shutdown = function( pattern )
		return shutdown( socket, pattern )
	end
	handler.setoption = function (self, option, value)
		if socket.setoption then
			return socket:setoption(option, value);
		end
		return false, "setoption not implemented";
	end
	handler.force_close = function ( self, err )
		if bufferqueuelen ~= 0 then
			out_put("server.lua: discarding unwritten data for ", tostring(ip), ":", tostring(clientport))
			for i = bufferqueuelen, 1, -1 do
				bufferqueue[i] = nil;
			end
			bufferqueuelen = 0;
		end
		return self:close(err);
	end
	handler.close = function( self, err )
		if not handler then return true; end
		_readlistlen = removesocket( _readlist, socket, _readlistlen )
		_readtimes[ handler ] = nil
		if bufferqueuelen ~= 0 then
			handler.sendbuffer() -- Try now to send any outstanding data
			if bufferqueuelen ~= 0 then -- Still not empty, so we'll try again later
				if handler then
					handler.write = nil -- ... but no further writing allowed
				end
				toclose = true
				return false
			end
		end
		if socket then
			_ = shutdown and shutdown( socket )
			socket:close( )
			_sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
			_socketlist[ socket ] = nil
			socket = nil
		else
			out_put "server.lua: socket already closed"
		end
		if handler then
			_writetimes[ handler ] = nil
			_closelist[ handler ] = nil
			local _handler = handler;
			handler = nil
			if disconnect then
				disconnect(_handler, err or false);
				disconnect = nil
			end
		end
		if server then
			server.remove( )
		end
		out_put "server.lua: closed client handler and removed socket from list"
		return true
	end
	handler.ip = function( )
		return ip
	end
	handler.serverport = function( )
		return serverport
	end
	handler.clientport = function( )
		return clientport
	end
	local write = function( self, data )
		bufferlen = bufferlen + string_len( data )
		if bufferlen > maxsendlen then
			_closelist[ handler ] = "send buffer exceeded"	 -- cannot close the client at the moment, have to wait to the end of the cycle
			handler.write = idfalse -- dont write anymore
			return false
		elseif socket and not _sendlist[ socket ] then
			_sendlistlen = addsocket(_sendlist, socket, _sendlistlen)
		end
		bufferqueuelen = bufferqueuelen + 1
		bufferqueue[ bufferqueuelen ] = data
		if handler then
			_writetimes[ handler ] = _writetimes[ handler ] or _currenttime
		end
		return true
	end
	handler.write = write
	handler.bufferqueue = function( self )
		return bufferqueue
	end
	handler.socket = function( self )
		return socket
	end
	handler.set_mode = function( self, new )
		pattern = new or pattern
		return pattern
	end
	handler.set_send = function ( self, newsend )
		send = newsend or send
		return send
	end
	handler.bufferlen = function( self, readlen, sendlen )
		maxsendlen = sendlen or maxsendlen
		maxreadlen = readlen or maxreadlen
		return bufferlen, maxreadlen, maxsendlen
	end
	--TODO: Deprecate
	handler.lock_read = function (self, switch)
		if switch == true then
			local tmp = _readlistlen
			_readlistlen = removesocket( _readlist, socket, _readlistlen )
			_readtimes[ handler ] = nil
			if _readlistlen ~= tmp then
				noread = true
			end
		elseif switch == false then
			if noread then
				noread = false
				_readlistlen = addsocket(_readlist, socket, _readlistlen)
				_readtimes[ handler ] = _currenttime
			end
		end
		return noread
	end
	handler.pause = function (self)
		return self:lock_read(true);
	end
	handler.resume = function (self)
		return self:lock_read(false);
	end
	handler.lock = function( self, switch )
		handler.lock_read (switch)
		if switch == true then
			handler.write = idfalse
			local tmp = _sendlistlen
			_sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
			_writetimes[ handler ] = nil
			if _sendlistlen ~= tmp then
				nosend = true
			end
		elseif switch == false then
			handler.write = write
			if nosend then
				nosend = false
				write( "" )
			end
		end
		return noread, nosend
	end
	local _readbuffer = function( ) -- this function reads data
		local buffer, err, part = receive( socket, pattern )	-- receive buffer with "pattern"
		if not err or (err == "wantread" or err == "timeout") then -- received something
			local buffer = buffer or part or ""
			local len = string_len( buffer )
			if len > maxreadlen then
				handler:close( "receive buffer exceeded" )
				return false
			end
			local count = len * STAT_UNIT
			readtraffic = readtraffic + count
			_readtraffic = _readtraffic + count
			_readtimes[ handler ] = _currenttime
			--out_put( "server.lua: read data '", buffer:gsub("[^%w%p ]", "."), "', error: ", err )
			return dispatch( handler, buffer, err )
		else	-- connections was closed or fatal error
			out_put( "server.lua: client ", tostring(ip), ":", tostring(clientport), " read error: ", tostring(err) )
			fatalerror = true
			_ = handler and handler:force_close( err )
			return false
		end
	end
	local _sendbuffer = function( ) -- this function sends data
		local succ, err, byte, buffer, count;
		if socket then
			buffer = table_concat( bufferqueue, "", 1, bufferqueuelen )
			succ, err, byte = send( socket, buffer, 1, bufferlen )
			count = ( succ or byte or 0 ) * STAT_UNIT
			sendtraffic = sendtraffic + count
			_sendtraffic = _sendtraffic + count
			_ = _cleanqueue and clean( bufferqueue )
			--out_put( "server.lua: sended '", buffer, "', bytes: ", tostring(succ), ", error: ", tostring(err), ", part: ", tostring(byte), ", to: ", tostring(ip), ":", tostring(clientport) )
		else
			succ, err, count = false, "unexpected close", 0;
		end
		if succ then	-- sending succesful
			bufferqueuelen = 0
			bufferlen = 0
			_sendlistlen = removesocket( _sendlist, socket, _sendlistlen ) -- delete socket from writelist
			_writetimes[ handler ] = nil
			if drain then
				drain(handler)
			end
			_ = needtls and handler:starttls(nil)
			_ = toclose and handler:force_close( )
			return true
		elseif byte and ( err == "timeout" or err == "wantwrite" ) then -- want write
			buffer = string_sub( buffer, byte + 1, bufferlen ) -- new buffer
			bufferqueue[ 1 ] = buffer	 -- insert new buffer in queue
			bufferqueuelen = 1
			bufferlen = bufferlen - byte
			_writetimes[ handler ] = _currenttime
			return true
		else	-- connection was closed during sending or fatal error
			out_put( "server.lua: client ", tostring(ip), ":", tostring(clientport), " write error: ", tostring(err) )
			fatalerror = true
			_ = handler and handler:force_close( err )
			return false
		end
	end

	-- Set the sslctx
	local handshake;
	function handler.set_sslctx(self, new_sslctx)
		sslctx = new_sslctx;
		local read, wrote
		handshake = coroutine_wrap( function( client ) -- create handshake coroutine
				local err
				for i = 1, _maxsslhandshake do
					_sendlistlen = ( wrote and removesocket( _sendlist, client, _sendlistlen ) ) or _sendlistlen
					_readlistlen = ( read and removesocket( _readlist, client, _readlistlen ) ) or _readlistlen
					read, wrote = nil, nil
					_, err = client:dohandshake( )
					if not err then
						out_put( "server.lua: ssl handshake done" )
						handler.readbuffer = _readbuffer	-- when handshake is done, replace the handshake function with regular functions
						handler.sendbuffer = _sendbuffer
						_ = status and status( handler, "ssl-handshake-complete" )
						if self.autostart_ssl and listeners.onconnect then
							listeners.onconnect(self);
						end
						_readlistlen = addsocket(_readlist, client, _readlistlen)
						return true
					else
						if err == "wantwrite" then
							_sendlistlen = addsocket(_sendlist, client, _sendlistlen)
							wrote = true
						elseif err == "wantread" then
							_readlistlen = addsocket(_readlist, client, _readlistlen)
							read = true
						else
							break;
						end
						err = nil;
						coroutine_yield( ) -- handshake not finished
					end
				end
				out_put( "server.lua: ssl handshake error: ", tostring(err or "handshake too long") )
				_ = handler and handler:force_close("ssl handshake failed")
               return false, err -- handshake failed
			end
		)
	end
	if luasec then
		handler.starttls = function( self, _sslctx)
			if _sslctx then
				handler:set_sslctx(_sslctx);
			end
			if bufferqueuelen > 0 then
				out_put "server.lua: we need to do tls, but delaying until send buffer empty"
				needtls = true
				return
			end
			out_put( "server.lua: attempting to start tls on " .. tostring( socket ) )
			local oldsocket, err = socket
			socket, err = ssl_wrap( socket, sslctx )	-- wrap socket
			if not socket then
				out_put( "server.lua: error while starting tls on client: ", tostring(err or "unknown error") )
				return nil, err -- fatal error
			end

			socket:settimeout( 0 )

			-- add the new socket to our system
			send = socket.send
			receive = socket.receive
			shutdown = id
			_socketlist[ socket ] = handler
			_readlistlen = addsocket(_readlist, socket, _readlistlen)
			
			-- remove traces of the old socket
			_readlistlen = removesocket( _readlist, oldsocket, _readlistlen )
			_sendlistlen = removesocket( _sendlist, oldsocket, _sendlistlen )
			_socketlist[ oldsocket ] = nil

			handler.starttls = nil
			needtls = nil

			-- Secure now (if handshake fails connection will close)
			ssl = true

			handler.readbuffer = handshake
			handler.sendbuffer = handshake
                       return handshake( socket ) -- do handshake
		end
	end

	handler.readbuffer = _readbuffer
	handler.sendbuffer = _sendbuffer
	send = socket.send
	receive = socket.receive
	shutdown = ( ssl and id ) or socket.shutdown

	_socketlist[ socket ] = handler
	_readlistlen = addsocket(_readlist, socket, _readlistlen)

	if sslctx and luasec then
		out_put "server.lua: auto-starting ssl negotiation..."
		handler.autostart_ssl = true;
               local ok, err = handler:starttls(sslctx);
               if ok == false then
                       return nil, nil, err
               end
	end

	return handler, socket
end

id = function( )
end

idfalse = function( )
	return false
end

addsocket = function( list, socket, len )
	if not list[ socket ] then
		len = len + 1
		list[ len ] = socket
		list[ socket ] = len
	end
	return len;
end

removesocket = function( list, socket, len )	-- this function removes sockets from a list ( copied from copas )
	local pos = list[ socket ]
	if pos then
		list[ socket ] = nil
		local last = list[ len ]
		list[ len ] = nil
		if last ~= socket then
			list[ last ] = pos
			list[ pos ] = last
		end
		return len - 1
	end
	return len
end

closesocket = function( socket )
	_sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
	_readlistlen = removesocket( _readlist, socket, _readlistlen )
	_socketlist[ socket ] = nil
	socket:close( )
	--mem_free( )
end

local function link(sender, receiver, buffersize)
	local sender_locked;
	local _sendbuffer = receiver.sendbuffer;
	function receiver.sendbuffer()
		_sendbuffer();
		if sender_locked and receiver.bufferlen() < buffersize then
			sender:lock_read(false); -- Unlock now
			sender_locked = nil;
		end
	end
	
	local _readbuffer = sender.readbuffer;
	function sender.readbuffer()
		_readbuffer();
		if not sender_locked and receiver.bufferlen() >= buffersize then
			sender_locked = true;
			sender:lock_read(true);
		end
	end
end

----------------------------------// PUBLIC //--

addserver = function( addr, port, listeners, pattern, sslctx ) -- this function provides a way for other scripts to reg a server
	local err
	if type( listeners ) ~= "table" then
		err = "invalid listener table"
	end
	if type( port ) ~= "number" or not ( port >= 0 and port <= 65535 ) then
		err = "invalid port"
	elseif _server[ addr..":"..port ] then
		err = "listeners on '[" .. addr .. "]:" .. port .. "' already exist"
	elseif sslctx and not luasec then
		err = "luasec not found"
	end
	if err then
		out_error( "server.lua, [", addr, "]:", port, ": ", err )
		return nil, err
	end
	addr = addr or "*"
	local server, err = socket_bind( addr, port )
	if err then
		out_error( "server.lua, [", addr, "]:", port, ": ", err )
		return nil, err
	end
	local handler, err = wrapserver( listeners, server, addr, port, pattern, sslctx, _maxclientsperserver ) -- wrap new server socket
	if not handler then
		server:close( )
		return nil, err
	end
	server:settimeout( 0 )
	_readlistlen = addsocket(_readlist, server, _readlistlen)
	_server[ addr..":"..port ] = handler
	_socketlist[ server ] = handler
	out_put( "server.lua: new "..(sslctx and "ssl " or "").."server listener on '[", addr, "]:", port, "'" )
	return handler
end

getserver = function ( addr, port )
	return _server[ addr..":"..port ];
end

removeserver = function( addr, port )
	local handler = _server[ addr..":"..port ]
	if not handler then
		return nil, "no server found on '[" .. addr .. "]:" .. tostring( port ) .. "'"
	end
	handler:close( )
	_server[ addr..":"..port ] = nil
	return true
end

closeall = function( )
	for _, handler in pairs( _socketlist ) do
		handler:close( )
		_socketlist[ _ ] = nil
	end
	_readlistlen = 0
	_sendlistlen = 0
	_timerlistlen = 0
	_server = { }
	_readlist = { }
	_sendlist = { }
	_timerlist = { }
	_socketlist = { }
	--mem_free( )
end

getsettings = function( )
	return	_selecttimeout, _sleeptime, _maxsendlen, _maxreadlen, _checkinterval, _sendtimeout, _readtimeout, _cleanqueue, _maxclientsperserver, _maxsslhandshake
end

changesettings = function( new )
	if type( new ) ~= "table" then
		return nil, "invalid settings table"
	end
	_selecttimeout = tonumber( new.select_timeout ) or _selecttimeout
	_sleeptime = tonumber( new.select_sleep_time ) or _sleeptime
	_maxsendlen = tonumber( new.max_send_buffer_size ) or _maxsendlen
	_maxreadlen = tonumber( new.max_receive_buffer_size ) or _maxreadlen
	_checkinterval = tonumber( new.select_idle_check_interval ) or _checkinterval
	_sendtimeout = tonumber( new.send_timeout ) or _sendtimeout
	_readtimeout = tonumber( new.read_timeout ) or _readtimeout
	_cleanqueue = new.select_clean_queue
	_maxclientsperserver = new.max_connections or _maxclientsperserver
	_maxsslhandshake = new.max_ssl_handshake_roundtrips or _maxsslhandshake
	return true
end

addtimer = function( listener )
	if type( listener ) ~= "function" then
		return nil, "invalid listener function"
	end
	_timerlistlen = _timerlistlen + 1
	_timerlist[ _timerlistlen ] = listener
	return true
end

stats = function( )
	return _readtraffic, _sendtraffic, _readlistlen, _sendlistlen, _timerlistlen
end

local quitting;

local function setquitting(quit)
	quitting = not not quit;
end

loop = function(once) -- this is the main loop of the program
	if quitting then return "quitting"; end
	if once then quitting = "once"; end
	local next_timer_time = math_huge;
	repeat
		local read, write, err = socket_select( _readlist, _sendlist, math_min(_selecttimeout, next_timer_time) )
		for i, socket in ipairs( write ) do -- send data waiting in writequeues
			local handler = _socketlist[ socket ]
			if handler then
				handler.sendbuffer( )
			else
				closesocket( socket )
				out_put "server.lua: found no handler and closed socket (writelist)"	-- this should not happen
			end
		end
		for i, socket in ipairs( read ) do -- receive data
			local handler = _socketlist[ socket ]
			if handler then
				handler.readbuffer( )
			else
				closesocket( socket )
				out_put "server.lua: found no handler and closed socket (readlist)" -- this can happen
			end
		end
		for handler, err in pairs( _closelist ) do
			handler.disconnect( )( handler, err )
			handler:force_close()	 -- forced disconnect
		end
		clean( _closelist )
		_currenttime = luasocket_gettime( )
		if _currenttime - _timer >= math_min(next_timer_time, 1) then
			next_timer_time = math_huge;
			for i = 1, _timerlistlen do
				local t = _timerlist[ i ]( _currenttime ) -- fire timers
				if t then next_timer_time = math_min(next_timer_time, t); end
			end
			_timer = _currenttime
		else
			next_timer_time = next_timer_time - (_currenttime - _timer);
		end
		socket_sleep( _sleeptime ) -- wait some time
		--collectgarbage( )
	until quitting;
	if once and quitting == "once" then quitting = nil; return; end
	return "quitting"
end

local function step()
	return loop(true);
end

local function get_backend()
	return "select";
end

--// EXPERIMENTAL //--

local wrapclient = function( socket, ip, serverport, listeners, pattern, sslctx )
	local handler = wrapconnection( nil, listeners, socket, ip, serverport, "clientport", pattern, sslctx )
	_socketlist[ socket ] = handler
	if not sslctx then
		_sendlistlen = addsocket(_sendlist, socket, _sendlistlen)
		if listeners.onconnect then
			-- When socket is writeable, call onconnect
			local _sendbuffer = handler.sendbuffer;
			handler.sendbuffer = function ()
				_sendlistlen = removesocket( _sendlist, socket, _sendlistlen );
				handler.sendbuffer = _sendbuffer;
				listeners.onconnect(handler);
				-- If there was data with the incoming packet, handle it now.
				if #handler:bufferqueue() > 0 then
					return _sendbuffer();
				end
			end
		end
	end
	return handler, socket
end

local addclient = function( address, port, listeners, pattern, sslctx )
	local client, err = luasocket.tcp( )
	if err then
		return nil, err
	end
	client:settimeout( 0 )
	_, err = client:connect( address, port )
	if err then -- try again
		local handler = wrapclient( client, address, port, listeners )
	else
		wrapconnection( nil, listeners, client, address, port, "clientport", pattern, sslctx )
	end
end

--// EXPERIMENTAL //--

----------------------------------// BEGIN //--

use "setmetatable" ( _socketlist, { __mode = "k" } )
use "setmetatable" ( _readtimes, { __mode = "k" } )
use "setmetatable" ( _writetimes, { __mode = "k" } )

_timer = luasocket_gettime( )
_starttime = luasocket_gettime( )

addtimer( function( )
		local difftime = os_difftime( _currenttime - _starttime )
		if difftime > _checkinterval then
			_starttime = _currenttime
			for handler, timestamp in pairs( _writetimes ) do
				if os_difftime( _currenttime - timestamp ) > _sendtimeout then
					--_writetimes[ handler ] = nil
					handler.disconnect( )( handler, "send timeout" )
					handler:force_close()	 -- forced disconnect
				end
			end
			for handler, timestamp in pairs( _readtimes ) do
				if os_difftime( _currenttime - timestamp ) > _readtimeout then
					--_readtimes[ handler ] = nil
					handler.disconnect( )( handler, "read timeout" )
					handler:close( )	-- forced disconnect?
				end
			end
		end
	end
)

local function setlogger(new_logger)
	local old_logger = log;
	if new_logger then
		log = new_logger;
	end
	return old_logger;
end

----------------------------------// PUBLIC INTERFACE //--

return {
	_addtimer = addtimer,

	addclient = addclient,
	wrapclient = wrapclient,
	
	loop = loop,
	link = link,
	step = step,
	stats = stats,
	closeall = closeall,
	addserver = addserver,
	getserver = getserver,
	setlogger = setlogger,
	getsettings = getsettings,
	setquitting = setquitting,
	removeserver = removeserver,
	get_backend = get_backend,
	changesettings = changesettings,
}