Clean your mesh net with some mild dish-washing soap and water to remove any dirt. Allow it to air dry for 24 hours to ensure it is fully dry before proceeding. If your net comes with specific instructions for mesh washing, follow these instead, but mild soap shouldn't harm mesh in most cases.
Open a can of wood sealant and dip the hanging pocket of your mesh net into the liquid, stopping about 2 inches from the frame of your stick. Lift up and let excess sealant drip off on some newspaper. Make sure not to dip any of the plastic or metal frame off your stick into the sealant.
Holding your net out in front of you and still over newspaper, dip a 1-inch paintbrush into the wood sealant and paint the areas of the mesh that didn't get dipped in the sealant around the frame of your stick. Again, be careful not to get sealant on the actual frame, and wipe off any areas that get splattered with a wet cloth.
Stand your net up and let it dry for eight hours, then repeat Steps 2 and 3 and let your net dry for 24 hours. If you still want your mesh to be harder, you can apply more coats -- just let each coat dry thoroughly.