How to get local IP address in javascript html5

Given from here you can do that.

/**
 * Get the user IP throught the webkitRTCPeerConnection
 * @param onNewIP {Function} listener function to expose the IP locally
 * @return undefined
 */
function getUserIP(onNewIP) { //  onNewIp - your listener function for new IPs
    //compatibility for firefox and chrome
    var myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
    var pc = new myPeerConnection({
        iceServers: []
    }),
    noop = function() {},
    localIPs = {},
    ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/g,
    key;

    function iterateIP(ip) {
        if (!localIPs[ip]) onNewIP(ip);
        localIPs[ip] = true;
    }

     //create a bogus data channel
    pc.createDataChannel("");

    // create offer and set local description
    pc.createOffer().then(function(sdp) {
        sdp.sdp.split('\n').forEach(function(line) {
            if (line.indexOf('candidate') < 0) return;
            line.match(ipRegex).forEach(iterateIP);
        });

        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(ipRegex)) return;
        ice.candidate.candidate.match(ipRegex).forEach(iterateIP);
    };
}

// Usage

getUserIP(function(ip){
    alert("Got IP! :" + ip);
});

I dont think that there is a notion of hosts or ip-addresses in the javascript standard library. So you'll have to access some external service to look up hostnames for you.

Unless you might want to send a request to the server which returns you the host IP address!!

EDIT

In JSP you you can use getRemoteHost() method from HttpServletRequest

to get the IP address of the user.

So you can write something like this -

var ip = '<%=request.getRemoteHost();%>'; 

^^ the above line is JSP code, this should be part of the JSP file that you return from java servlet container like a tomcat. This does not work in static HTML pages.