when I parse .pcap file I got gibberish

when I parse .pcap file I got gibberish, I don't know which step wrong, please

help me, thank you!

1.I use tcpdump to monitor cn.bing.com, then save file demo.pcap

sudo tcpdump -i en0 -nn -q  host cn.bing.com -w /Users/gyk/desktop/demo.pcap

2.I use npm module pcap-parser to parse demo.pcap

var pcapp = require('pcap-parser');

var parser = pcapp.parse('/Users/gyk/desktop/test.pcap');

// packet { header: {...}, data: Buffer}
parser.on('packet', function(packet) {
    console.log(packet.data.toString())
}

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