The client receives data with garbage at the beginning via a web socket. How to fix?

Question

PHP

I wanted to do a websocket connection test. I connect to the server through swoole. I get a handshake, everything is ok, the connection is stable. Connecting returns a response from the server with connection data, but any data I get from the server has garbage characters at the beginning. If you connect to the server via Postman, then the data is clean and everything is ok. I don't understand what could be the problem.

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