diff --git a/js/tools/build/ndn-js-uncomp.js b/js/tools/build/ndn-js-uncomp.js
index 31c3998..b947a5c 100644
--- a/js/tools/build/ndn-js-uncomp.js
+++ b/js/tools/build/ndn-js-uncomp.js
@@ -69,6 +69,9 @@
  */
 
 var WebSocketTransport = function WebSocketTransport() {    
+    if (!WebSocket)
+        throw new Error("WebSocket support is not available on this platform.");
+    
 	this.ws = null;
     this.connectedHost = null; // Read by NDN.
     this.connectedPort = null; // Read by NDN.
diff --git a/js/tools/build/ndn-js.js b/js/tools/build/ndn-js.js
index 1aadee6..fb403f1 100644
--- a/js/tools/build/ndn-js.js
+++ b/js/tools/build/ndn-js.js
@@ -1,6 +1,6 @@
 var Closure=function(){this.ndn_data=null;this.ndn_data_dirty=!1};Closure.RESULT_ERR=-1;Closure.RESULT_OK=0;Closure.RESULT_REEXPRESS=1;Closure.RESULT_INTEREST_CONSUMED=2;Closure.RESULT_VERIFY=3;Closure.RESULT_FETCHKEY=4;Closure.UPCALL_FINAL=0;Closure.UPCALL_INTEREST=1;Closure.UPCALL_CONSUMED_INTEREST=2;Closure.UPCALL_CONTENT=3;Closure.UPCALL_INTEREST_TIMED_OUT=4;Closure.UPCALL_CONTENT_UNVERIFIED=5;Closure.UPCALL_CONTENT_BAD=6;Closure.prototype.upcall=function(){return Closure.RESULT_OK};
 var UpcallInfo=function(a,b,c,d){this.ndn=a;this.interest=b;this.matchedComps=c;this.contentObject=d};UpcallInfo.prototype.toString=function(){var a="ndn = "+this.ndn,a=a+("\nInterest = "+this.interest),a=a+("\nmatchedComps = "+this.matchedComps);return a+="\nContentObject: "+this.contentObject};
-var WebSocketTransport=function(){this.elementReader=this.connectedPort=this.connectedHost=this.ws=null;this.defaultGetHostAndPort=NDN.makeShuffledGetHostAndPort(["A.ws.ndn.ucla.edu","B.ws.ndn.ucla.edu","C.ws.ndn.ucla.edu","D.ws.ndn.ucla.edu","E.ws.ndn.ucla.edu"],9696)};
+var WebSocketTransport=function(){if(!WebSocket)throw Error("WebSocket support is not available on this platform.");this.elementReader=this.connectedPort=this.connectedHost=this.ws=null;this.defaultGetHostAndPort=NDN.makeShuffledGetHostAndPort(["A.ws.ndn.ucla.edu","B.ws.ndn.ucla.edu","C.ws.ndn.ucla.edu","D.ws.ndn.ucla.edu","E.ws.ndn.ucla.edu"],9696)};
 WebSocketTransport.prototype.connect=function(a,b){null!=this.ws&&delete this.ws;this.ws=new WebSocket("ws://"+a.host+":"+a.port);0<LOG&&console.log("ws connection created.");this.connectedHost=a.host;this.connectedPort=a.port;this.ws.binaryType="arraybuffer";this.elementReader=new BinaryXmlElementReader(a);var c=this;this.ws.onmessage=function(a){a=a.data;if(null==a||void 0==a||""==a)console.log("INVALID ANSWER");else if(a instanceof ArrayBuffer){a=new Uint8Array(a);3<LOG&&console.log("BINARY RESPONSE IS "+
 DataUtils.toHex(a));try{c.elementReader.onReceivedData(a)}catch(b){console.log("NDN.ws.onmessage exception: "+b)}}};this.ws.onopen=function(a){3<LOG&&console.log(a);3<LOG&&console.log("ws.onopen: WebSocket connection opened.");3<LOG&&console.log("ws.onopen: ReadyState: "+this.readyState);b()};this.ws.onerror=function(a){console.log("ws.onerror: ReadyState: "+this.readyState);console.log(a);console.log("ws.onerror: WebSocket error: "+a.data)};this.ws.onclose=function(){console.log("ws.onclose: WebSocket connection closed.");
 c.ws=null;a.readyStatus=NDN.CLOSED;a.onclose()}};WebSocketTransport.prototype.send=function(a){if(null!=this.ws){var b=new Uint8Array(a.length);b.set(a);this.ws.send(b.buffer);3<LOG&&console.log("ws.send() returned.")}else console.log("WebSocket connection is not established.")};