So, it all started with a requirement for my website when I needed to get the client’s IP address for some security purposes. It felt like an easy task in the beginning but after some time, I realized that most of the available methods of getting an IP address return the Server’s IP Address and not the local IP address of the client. And, there are some APIs which return your Public IP address but again, none of them returns the local IP address. So, we will see how we can achieve that.

Using JavaScript

In JavaScript, you can use the following script for getting the IP address.

< script >  
    var RTCPeerConnection = /*window.RTCPeerConnection ||*/ window.webkitRTCPeerConnection || window.mozRTCPeerConnection;  
if (RTCPeerConnection)(function() {  
    var rtc = new RTCPeerConnection({  
        iceServers: []  
    });  
    if (1 || window.mozRTCPeerConnection) {  
        rtc.createDataChannel('', {  
            reliable: false  
        });  
    };  
    rtc.onicecandidate = function(evt) {  
        if (evt.candidate) grepSDP("a=" + evt.candidate.candidate);  
    };  
    rtc.createOffer(function(offerDesc) {  
        grepSDP(offerDesc.sdp);  
        rtc.setLocalDescription(offerDesc);  
    }, function(e) {  
        console.warn("offer failed", e);  
    });  
    var addrs = Object.create(null);  
    addrs["0.0.0.0"] = false;  

    function updateDisplay(newAddr) {  
        if (newAddr in addrs) return;  
        else addrs[newAddr] = true;  
        var displayAddrs = Object.keys(addrs).filter(function(k) {  
            return addrs[k];  
        });  
        document.getElementById('list').textContent = displayAddrs.join(" or perhaps ") || "n/a";  
    }  

    function grepSDP(sdp) {  
        var hosts = [];  
        sdp.split('\r\n').forEach(function(line) {  
            if (~line.indexOf("a=candidate")) {  
                var parts = line.split(' '),  
                    addr = parts[4],  
                    type = parts[7];  
                if (type === 'host') updateDisplay(addr);  
            } else if (~line.indexOf("c=")) {  
                var parts = line.split(' '),  
                    addr = parts[2];  
                updateDisplay(addr);  
            }  
        });  
    }  
})();  
else {  
    document.getElementById('list').innerHTML = "<code>ifconfig| grep inet | grep -v inet6 | cut -d\" \" -f2 | tail -n1</code>";  
    document.getElementById('list').nextSibling.textContent = "In Chrome and Firefox your IP should display automatically, by the power of WebRTCskull.";  
} < /script>   

#javascript #programming