Connector for fastener for Christmas light strings

A connector and fastener are used particularly for a Christmas light string. The connector has a wire holding portion and a socket-engaging portion. Locking keys are formed on the wire holding portion and receiving holes are formed on the receiving portion for engagement with said locking keys when said wire holding portion is inserted into said socket-engaging portion. The fastener has at least one snapping element disposed on a socket of another Christmas light string and a corresponding number of flat tongues formed on the outer periphery of said connector for snap fitting when said connector is engaged with said socket. The connector may be configured to connect two wires respectively to two Christmas light strings or may be a connector with a socket to be inserted with another connector or an electrical gadget.