A socket and a plug are provided. Both the socket and the plug include a body, a blocking sheet, and an elastic member. Both the bodies define a coupling portion. The blocking sheet is disposed on the corresponding body and covers the corresponding coupling portion to protect the coupling portions from being contaminated when not used. The elastic member connects the corresponding body and the blocking sheet. When the plug is plugged into the socket, the blocking sheets, against an elastic force of the elastic member, pushes each other to expose the coupling portions until the coupling portions are coupled.