How can I send data from Server to Client without GET request from the client?

(Sorry for my bad english)

Hi! I asking me a question... If I want to create a chatting web-application with NodeJS, how can I send data from the server to the client without GET request from the client ?

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(example)

That I want :

Server - WRITE -> Client

That I know :

Client - GET -> Server - WRITE -> Client

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The major problem with the second one is that I need to refresh data all the time. I search for a solution OTHER than Socket.IO, but it seems to be impossible or very complicated :/

Please help me :c !