Close #9 Implement keep-alive mechanism

README.md

@@ -34,7 +34,6 @@ The constructor takes 3 parameters. If you want to make use of the `connect` opt
 
 **INFO**: The raw socket can be accessed via the instance's `sock` property.
 
-
 ## Sending Commands
 #### TeamspeakQuery.send(cmd, params?, ...flags?)
 Sends a command to the server and returns a Promise that resolves the response or rejects if something went wrong.
@@ -46,6 +45,14 @@ You can also use it to set flags, e.g. `query.send('clientlist', '-uid')`.
 
 If you want your response to be an array, e.g. for commands like `clientlist`, take a look at [Issue #3](https://github.com/schroffl/teamspeak-query/issues/3#issuecomment-359252099).
 
+## Keep-Alive
+A keep-alive mechanism is implemented to prevent the server from closing the connection after inactivity. It basically just sends a `version` command every few minutes (This doesn't require authentication and has a very small overhead).
+If you want to tune its parameters, you can access the `keepalive` property of your `TeamspeakQuery` instance:
+```javascript
+query.keepalive.enable(true); // true => enable, false => disable, (default: true)
+query.keepalive.duration = 30000; // Send the command every 30 seconds, (default: 5 minutes)
+```
+
 ## Throttling
 Commands are being throttled by default if the host is not set to the local machine (`127.0.0.1` or `localhost`) in order to prevent a ban for flooding (see [Whitelisting and Blacklisting](http://media.teamspeak.com/ts3_literature/TeamSpeak%203%20Server%20Query%20Manual.pdf?#page=6) on page 6 in the specs).  
 The instance of [lib/throttle.js](lib/throttle.js) can be accessed via `TeamspeakQuery.throttle`.  

index.js

@@ -7,6 +7,7 @@ const type = require('type-of');
 const carrier = require('carrier');
 
 const Throttle = require('./lib/throttle');
+const KeepAlive = require('./lib/keepalive');
 
 class TeamspeakQuery extends EventEmitter {
 
@@ -41,9 +42,14 @@ class TeamspeakQuery extends EventEmitter {
       'enable': connectOptions.host !== '127.0.0.1' && connectOptions.host !== 'localhost'
     });
 
+    this.keepalive = new KeepAlive(() => this.send('version'));
+    this.keepalive.enable(false);
+
     sock.connect(connectOptions);
 
     sock.on('connect', () => {
+      this.keepalive.enable(true);
+
       this.carrier = carrier.carry(sock);
       this.carrier.on('line', this.handleLine.bind(this));
     });
@@ -73,6 +79,8 @@ class TeamspeakQuery extends EventEmitter {
   checkQueue() {
     this.throttle.run(() => {
       if(!this._current && this.queue.length) {
+        this.keepalive.interrupt();
+
         this._current = this.queue.shift();
         this.sock.write(this._current.cmd + '\n');
       }