Have a default port and only switch to a random one if that's taken

portInUse.js

@@ -0,0 +1,18 @@
+const net = require('net');
+
+module.exports = function(port, callback) {
+    const server = net.createServer(function(socket) {
+	socket.write('Echo server\r\n');
+	socket.pipe(socket);
+    })
+
+    server.listen(port, '127.0.0.1');
+    server.on('error', function (e) {
+	callback(true)
+    })
+    server.on('listening', function (e) {
+	server.close()
+	callback(false)
+    })
+}
+