choose port dynamically from range based on environment

src/services/env.js

@@ -0,0 +1,5 @@
+module.exports = {
+    isDev: function () {
+        return process.env.TRILIUM_ENV && process.env.TRILIUM_ENV === 'dev';
+    }
+};

src/services/port.js

@@ -1,10 +1,28 @@
-const getPort = require('get-port');
 const config = require('./config');
 const utils = require('./utils');
+const env = require('./env');
+const portscanner = require('portscanner');
+
+let environmentPort;
+
+if (process.env.TRILIUM_PORT) {
+    environmentPort = parseInt(process.env.TRILIUM_PORT);
+}
 
 if (utils.isElectron()) {
-    module.exports = 53010;//getPort();
+    module.exports = new Promise((resolve, reject) => {
+        const startingPort = environmentPort || (env.isDev() ? 37740 : 37840);
+
+        portscanner.findAPortNotInUse(startingPort, startingPort + 10, '127.0.0.1', function(error, port) {
+            if (error) {
+                reject(error);
+            }
+            else {
+                resolve(port);
+            }
+        })
+    });
 }
 else {
-    module.exports = Promise.resolve(config['Network']['port'] || '3000');
+    module.exports = Promise.resolve(environmentPort || config['Network']['port'] || '3000');
 }