Add ports in use warning to udp node

to close #786
Thanks @hugobox

nodes/core/io/32-udp.html

@@ -1,5 +1,5 @@
 <!--
-  Copyright 2013 IBM Corp.
+  Copyright 2013,2016 IBM Corp.
 
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
@@ -52,6 +52,7 @@
         <input type="text" id="node-input-name" data-i18n="[placeholder]common.label.name">
     </div>
     <div class="form-tips"><span data-i18n="udp.tip.in"></span></div>
+    <div class="form-tips" id="udpporttip"><span data-i18n="[html]udp.tip.port"></span></div>
 </script>
 
 <script type="text/x-red" data-help-name="udp in">
@@ -98,6 +99,21 @@
                 }
             });
             $("#node-input-multicast").change();
+
+            var porttip = this._("udp.tip.port");
+            var alreadyused = this._("udp.errors.alreadyused");
+            var portsInUse = {};
+            $.getJSON('udp-ports/'+this.id,function(data) {
+                portsInUse = data || {};
+                $('#udpporttip').html(porttip + Object.keys(data||{}));
+            });
+            $("#node-input-port").change(function() {
+                var portnew = $("#node-input-port").val();
+                if (portsInUse.hasOwnProperty($("#node-input-port").val())) {
+                    console.log($("#node-input-port").val());
+                    RED.notify(alreadyused+" "+$("#node-input-port").val(),"warn");
+                }
+            });
         }
     });
 </script>

nodes/core/io/32-udp.js

@@ -1,5 +1,5 @@
 /**
- * Copyright 2013 IBM Corp.
+ * Copyright 2013,2016 IBM Corp.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 module.exports = function(RED) {
     "use strict";
     var dgram = require('dgram');
+    var udpInputPortsInUse = {};
 
     // The Input Node
     function UDPin(n) {
@@ -28,6 +29,12 @@ module.exports = function(RED) {
         this.multicast = n.multicast;
         this.ipv = n.ipv || "udp4";
         var node = this;
+        if (!udpInputPortsInUse.hasOwnProperty(this.port)) {
+            udpInputPortsInUse[this.port] = n.id;
+        }
+        else {
+            node.warn(RED._("udp.errors.alreadyused",node.port));
+        }
 
         var opts = {type:node.ipv, reuseAddr:true};
         if (process.version.indexOf("v0.10") === 0) { opts = node.ipv; }
@@ -76,6 +83,10 @@ module.exports = function(RED) {
         });
 
         node.on("close", function() {
+            console.log("ID=",node.id);
+            if (udpInputPortsInUse[node.port] === node.id) {
+                delete udpInputPortsInUse[node.port];
+            }
             try {
                 server.close();
                 node.log(RED._("udp.status.listener-stopped"));
@@ -86,9 +97,11 @@ module.exports = function(RED) {
 
         server.bind(node.port,node.iface);
     }
+    RED.httpAdmin.get('/udp-ports/:id', RED.auth.needsPermission('udp-in.read'), function(req,res) {
+        res.json(udpInputPortsInUse);
+    });
     RED.nodes.registerType("udp in",UDPin);
 
-
     // The Output Node
     function UDPout(n) {
         RED.nodes.createNode(this,n);

nodes/core/locales/en-US/messages.json

@@ -398,7 +398,8 @@
         },
         "tip": {
             "in": "Tip: Make sure your firewall will allow the data in.",
-            "out": "Tip: leave address and port blank if you want to set using <b>msg.ip</b> and <b>msg.port</b>."
+            "out": "Tip: leave address and port blank if you want to set using <b>msg.ip</b> and <b>msg.port</b>.",
+            "port": "Ports already in use: "
         },
         "status": {
             "listener-at": "udp listener at __host__:__port__",
@@ -417,7 +418,8 @@
             "interface": "Must be ip address of the required interface",
             "ip-notset": "udp: ip address not set",
             "port-notset": "udp: port not set",
-            "port-invalid": "udp: port number not valid"
+            "port-invalid": "udp: port number not valid",
+            "alreadyused": "udp: port already in use"
         }
     },
     "switch": {