code: function(client, packet) {
              var ball_id = packet.readUInt32LE();
              var ball    = client.balls[ball_id] || new Ball(client, ball_id);
              ball.mine   = true;
              if(!client.my_balls.length) client.score = 0;
              client.my_balls.push(ball_id);
  
              if(client.debug >= 2)
                  client.log('my new ball: ' + ball_id);
  
              if(client.spawn_interval_id) {
                  if(client.debug >= 4)
                      client.log('detected new ball, disabling spawn() interval');
                  client.spawn_attempt = 0;
                  clearInterval(client.spawn_interval_id);
                  client.spawn_interval_id = 0;
              }
  
              client.emitEvent('myNewBall', ball_id);
          }
docs: new ID of your ball (when you join or press space)