44/chat,"Error decoding value"

[xfishernet]

I try to connect from the React.js frontend, but I get an error:

44/chat,"Error decoding value"

after this:

const socket = io('localhost:9000/chat', {
  query: 'user=aaa',
});

socket.emit('join room', {room: 'test'});

PS: java/multi-room-chat