A connector, in particular an RJ45 plug having: - a contact device, with - at least one cable contact by means of which an electric line of a cable can be electrically contacted, - a cable passage through which a cable can be passed into the interior of the contact device along a cable passage direction, and - at least one engagement apparatus; - a strain relief device with: - a sleeve through which the cable can be passed along the cable passage direction and can be arranged on the contact device with an arrangement side in the region of the cable passage, and that has at least one flexible finger which extends substantially parallel to the cable passage direction and can be bent along a bending direction oriented substantially perpendicular to the cable passage direction, and - a sleeve fastening device through which the cable can be passed along the cable passage direction and which is designed to accommodate the sleeve, at least sectionally, along the cable passage direction in a sleeve seat, and which has at least one engagement apparatus that is complementary with the engagement apparatus of the contact device; wherein the at least one complementary engagement apparatus of the sleeve fastening device can, by shifting along the cable passage direction, be brought into engagement at least with the associated engagement apparatus,, and wherein the at least one complimentary engagement apparatus and the at least one engagement apparatus of the contact device can be locked together relative to the contact device by rotating the sleeve fastening device about a rotary axis that is orientated substantially parallel to the cable passage direction, wherein the at least one flexible finger of the sleeve can be bent along the bending direction by the locking in order to mechanically contact the cable when the cable is passed through the sleeve along the cable passage direction, characterized in that the sleeve has a fastening apparatus that can latch or lock with a complimentary fastening apparatus of the contact device so that the sleeve can be fastened in an arrangement position on the contact device. - a contact device, with - at least one cable contact by means of which an electric line of a cable can be electrically contacted, - a cable passage through which a cable can be passed into the interior of the contact device along a cable passage direction, and - at least one engagement apparatus; - at least one cable contact by means of which an electric line of a cable can be electrically contacted, - a cable passage through which a cable can be passed into the interior of the contact device along a cable passage direction, and - at least one engagement apparatus; - a strain relief device with: - a sleeve through which the cable can be passed along the cable passage direction and can be arranged on the contact device with an arrangement side in the region of the cable passage, and that has at least one flexible finger which extends substantially parallel to the cable passage direction and can be bent along a bending direction oriented substantially perpendicular to the cable passage direction, and - a sleeve fastening device through which the cable can be passed along the cable passage direction and which is designed to accommodate the sleeve, at least sectionally, along the cable passage direction in a sleeve seat, and which has at least one engagement apparatus that is complementary with the engagement apparatus of the contact device; - a sleeve through which the cable can be passed along the cable passage direction and can be arranged on the contact device with an arrangement side in the region of the cable passage, and that has at least one flexible finger which extends substantially parallel to the cable passage direction and can be bent along a bending direction oriented substantially perpendicular to the cable passage direction, and - a sleeve fastening device through which the cable can be passed along the cable passage direction and which is designed to accommodate the sleeve, at least sectionally, along the cable passage direction in a sleeve seat, and which has at least one engagement apparatus that is complementary with the engagement apparatus of the contact device;