Xymon : how is data flow in case of xymon

Hi,

i have one doubt regarding data flow (communication) in case of xymon in the sense that server-client architecture of xymon follows push or pull of data ? In case of xymon as how data flows from server to clients or clients to server ? How the data of external ( extention/ custom scripts ) scripts is available with server. How xymon handles all tests data? does it (server) pulls all data from clients or clients sends their data to xymon? or there is two way data flow?

Akshar