code: public void presence(String channel, OnPresence callback)
  			throws OrtcNotConnectedException {
  		if (!this.isConnected) {
  			throw new OrtcNotConnectedException();
  		} else {
  			String presenceUrl = this.isCluster ? this.clusterUrl : this.url;
  
  			Ortc.presence(presenceUrl, this.isCluster, this.applicationKey,
  					this.authenticationToken, channel, callback);
  		}
  	}
docs: Gets the subscriptions in the specified channel and if active the first
  100 unique metadata.
  
  <pre>
  Ortc.presence(&quot;CHANNEL&quot;, new onPresence() {
  
  public void run(Exception error, Presence presence) {
  if (error != null) {
  System.out.println(error.getMessage());
  } else {
  System.out.println(&quot;Subscriptions - &quot; + presence.getSubscriptions());
  
  Iterator&lt;?&gt; metadataIterator = presence.getMetadata().entrySet()
  .iterator();
  while (metadataIterator.hasNext()) {
  Map.Entry&lt;String, Long&gt; entry = (Map.Entry&lt;String, Long&gt;) metadataIterator
  .next();
  System.out.println(entry.getKey() + &quot; - &quot; + entry.getValue());
  }
  }
  }
  });
  </pre>
  
  @param channel
  Channel with presence data active.
  @param callback
  Callback with error and result.
  @throws OrtcNotConnectedException