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function getLocalIP(callback) {
    var peerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
    var pc = new peerConnection({iceServers:[]});
    var noop = function() {};
    var localIPs = {};

    function ipCandidate(candidate) {
        var ip = (candidate.split(' ')[4]);
        localIPs[ip] = true;
    }

    pc.createDataChannel("");
    pc.createOffer().then(function(sdp) {
        sdp.sdp.split('\n').forEach(function(line) {
            if (line.indexOf('candidate') < 0) return;
            ipCandidate(line);
        });

        pc.setLocalDescription(sdp, noop, noop);
    }).catch(function(reason) {
        // An error occurred, so handle the failure to connect
    });

    // Listen for candidate events
    pc.onicecandidate = function(ice) {
        if (!ice || !ice.candidate || !ice.candidate.candidate || !ice.candidate.candidate.match(/^candidate/)) return;
        ipCandidate(ice.candidate.candidate);
    };

    pc.onicegatheringstatechange = function() {
        if (pc.iceGatheringState === 'complete') {
            var ips = Object.keys(localIPs);
            if (ips.length > 0) {
                callback(ips.join(', '));
            }
        }
    };
}

getLocalIP(function(ip) {
    console.log('Local IP address is: ', ip);
});