Server-side heartbeat response.

server/ricochet.js

@@ -233,6 +233,7 @@ Ricochet.prototype.onMessage = function(ws, rawBody) {
         }
 
         switch (message.type) {
+            case 'heartbeat': this.msgHeartbeat(ws); break;
             case 'newround': this.msgNewRound(); break;
             case 'objective': this.msgObjective(); break;
             case 'robots': this.msgRobots(); break;
@@ -247,6 +248,10 @@ Ricochet.prototype.onMessage = function(ws, rawBody) {
 };
 
 //===== Message handlers
+Ricochet.prototype.msgHeartbeat = function() {
+    this.messenger.messageOne(ws, { type: 'heartbeat' });
+};
+
 Ricochet.prototype.msgNewRound = function() {
     this.objective = this.freshObjective();
     this.state = STATE.PLAY;