How to send msg to specific user using AspNet core signalr

i am developing a chat app using aspnet core signalr and i want to send message to a particular user by his UserId that is in my database but unable to do this .when i am usini "Clients.Others" it working fine and pushing to all except sender. at client side Angular 6 im using. please suggest me both server and client side code to send msg from server to al connection of particular client"