We faced error WebSocket connection to 'wss:****' failed: The operation couldn’t be completed. (kNWErrorDomainPOSIX error 100 - Protocol error) with big websocket messages on iOS15 (production, not beta) if server responds with "Sec-WebSocket-Extensions: permessage-deflate; server_no_context_takeover; client_no_context_takeover", if there are no such headers or if message very small then all works fine.
Maybe there is a bug with websockets compression in WKWebView
Nikolai22
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