DLL sensors

Every time the sensor is to be checked the selected DLL file is called. The DLL must export one function:

function perform(para,msg:pchar):integer; stdcall;

para and msg are zero terminated strings. The allocated buffer for msg is 255 bytes, the DLL must make sure that fewer bytes are returned. Msg must be in the following format:

value:message

Value has to be an 32 bit integer and will be used as the resulting value for this sensor (e.g. bytes, milliseconds, etc.), message can be any string and will be stored in the database.

The integer return value of the perform function has to be one of the following values:

·      0 ok

·      1 warning

·      2 system error (e.g. a socket error)

·      3 protocol error (e.g. html returns a 404)

·      4 content error  (e.g. a webpage contains not a required word)

Warning: If the function call in the DLL does not return control it can block the system. Make sure to handle your own timeouts and build in a reliable error management. For this reason EXE sensors are recommended.