Additional async rewrite

lib/GlobalUdpSocket.js

@@ -0,0 +1,42 @@
+const dgram = require('dgram'),
+    HexUtil = require('./HexUtil');
+
+class GlobalUdpSocket {
+    constructor() {
+        this.socket = null;
+        this.callbacks = new Set();
+        this.debug = false;
+    }
+
+    _getSocket() {
+        if (!this.socket) {
+            const udpSocket = this.socket = dgram.createSocket('udp4');
+            udpSocket.unref();
+            udpSocket.bind();
+            udpSocket.on('message', (buffer, rinfo) => {
+                for (const cb of this.callbacks) {
+                    cb(rinfo.address, rinfo.port, buffer);
+                }
+            });
+            udpSocket.on('error', (e) => {
+                if (this.debug) {
+                    console.log("UDP ERROR: " + e);
+                }
+            });
+        }
+        return this.socket;
+    }
+
+    send(buffer, address, port) {
+        this._getSocket().send(buffer,0,buffer.length,port,address);
+    }
+
+    addCallback(callback) {
+        this.callbacks.add(callback);
+    }
+    removeCallback(callback) {
+        this.callbacks.delete(callback);
+    }
+}
+
+module.exports = GlobalUdpSocket;