Adapter device, bracket assembly compatible with both OCP card and PCIe card, and server

An adapter device, comprising:

• a chassis;
• a front-end bracket connected to a front end of the chassis, wherein the front-end bracket defines a first inserting port which is sized to receive an open compute project (OCP) card;
• an adapter assembly comprising an OCP interface, an adapter circuit board, and a PCIe interface, wherein the adapter circuit board is connected to a rear end of the chassis, the OCP interface opposite to the first inserting port is connected to the adapter circuit board, the PCIe interface is connected to an end away from the first inserting port of the adapter circuit board, the adapter circuit board is electrically connected between the OCP interface and the PCIe interface to realize interface conversion;
• and
• a rail assembly opposite to the first inserting port positioned between the front-end bracket and the OCP interface.