I put 3 droppers on the top of each other. The bottom one I powered with "pulsing" redstone signal using the comparator and the redstone torch. Output signal of the comparator I returned back to the side of this comparator. Then I switch the comparator, so the output signal started pulsate. In singleplayer mode this works as I assumed. When I put some items into the bottom dropper, those items were transfered into the middle dropper and then into the top one.

However, in multiplayer mode this wiring doesn't work. Items, which I put into the bottom dropper weren't transfered into the upper droppers.

BTW: In singleplayer mode this wiring works in both survival and creative mode.