Socket.io with mitmproxy

I use mitmproxy to capture socket.io websocket, and try to display the content. But I always get the following error. Can anyone give me some hints what is the problem?

127.0.0.1:52292: GET game.club/g_5_2/?EIO=3&transport=websocket
<< 101 Switching Protocols 0b
127.0.0.1:52292 <- WebSocket 1 message <- game.club:443/g_5_2/?EIO=3&transport=websocket
127.0.0.1:52292 <- WebSocket 1 message <- game.club:443/g_5_2/?EIO=3&transport=websocket
WebSocket connection closed by client: 1007 (message missing), ‘utf-8’ codec can’t decode byte 0xdb in position 2: invalid continuation byte
127.0.0.1:52292: clientdisconnect
127.0.0.1:52294: clientconnect
127.0.0.1:52294: GET game.club/g_5_2/?EIO=3&transport=websocket
<< 101 Switching Protocols 0b
127.0.0.1:52294 <- WebSocket 1 message <- game.club:443/g_5_2/?EIO=3&transport=websocket
127.0.0.1:52294 <- WebSocket 1 message <- game.club:443/g_5_2/?EIO=3&transport=websocket
WebSocket connection closed by client: 1005 (message missing),
127.0.0.1:52294: clientdisconnect
127.0.0.1:52296: clientconnect