The connector on the back of your PC that has 9 pins and is used for RS232 communication is a DE9. A DB9 would be one the size of the parallel printer port connector, but with only 9 pins in that "B"-sized shell.

Since these shells, of whatever size they are, should be connected to "frame" gnd, however, that's implemented, the "shock" you experience is probably due to inadequate grounding. If they are connected to earth-gnd, through a low-resistance cable, say, a 2-cm-wide copper braid, to a metal water pipe that actually runs through a considerable distance of earth, or the like, you'll have no such "shock".

If you're observing the "shock" at the far end of the cable from the running equipment, then the equipment-end of the cable needs to be grounded to earth, as does the remote end.

RE