Modbus TCP connection status

[leonidas]

Hello, 

Do anyone know a good way to detect if there is or there is no connection with Modbus TCP device?

Code:

require('luamodbus')

mb = luamodbus.rtu()
mb:open('/dev/RS485-1', 9600, 'E', 8, 1, 'H')
mb:connect()

mb:setslave(1)
mb:setresponsetimeout(100)

--                     --
-- some modbus reading --
--                     --

mb:close()

[admin]

mb:connect() will return nil plus error message when connection cannot be established. If it breaks afterwards then all read/write calls will act the same.