Problems reading UDP packets

I have data coming in from another computer, in the form of UDP packets, that I'd like to plot in real time. To do this I have setup a UDP object and set a callback to be fired everytime a packet is received. This works pretty well for a few moments. function u = strippedDownReceiver(varargin)

args.host = '10.121.43.56';
args.rxPort = 5000;
args.txPort = 10000; % shouldn't matter as we aren't txing
args.udpObjBufferSize = 1024*8;

% -------------------------------------------
%   Networking variables
% -------------------------------------------

u = [];
nPacket = 0;

% -------------------------------------------
%  Start Everything up
% -------------------------------------------

initNetwork();

% -------------------------------------------
%   Network and Buffer Related Function
% -------------------------------------------
    function initNetwork()
        u = udp(args.host, args.txPort, 'LocalPort', args.rxPort);
        set(u,'BytesAvailableFcn', @udpPacketRxCallback);
        fopen(u);
    end

      function udpPacketRxCallback(obj, event)

          data = fread(obj);
          %nPacket = nPacket + 1;
          %disp(['Packets recieved:', num2str(nPacket)]);
          disp('Packet read');
      end
  end

When I run the function the "Packet Read" message is displayed several times but eventually the message stop appearing. Using Wireshark I can verify that packets are in fact arriving on my machine. Also if I execute. fclose(u); fopen(u); the message appears again for a while but eventually stops again.

Am I doing something obviously wrong here? What is the right way to continue reading data off of the network without stuttering or stopping?