I went through many threads and no solution could fix the case.
Client upgraded Eikon DAPI library to the newest already.
Root cause was two ports(9000, 9060) were opened simultaneously and were in listening state after Eikon was launched. In this case, port 9060 was recorded in the file: AppData\Roaming\Thomson Reuters\Eikon API Proxy\.portInUse. Client changed the port to 9000 in portInUse file. However, it was rechanged back to 9060 after Eikon was restarted.
In my laptop, only port 9000 is opened after Eikon is started.
Why Eikon opened two ports in client side? Could anyone help to fix this issue?