patch client-side Meteor functions to print out the DDP messages. Add this somewhere in your client-side JS before Meteor.startup() and it should print out the DDP messages. Please let me know if there are some that are missing! I'm not sure I caught all of the handler functions.

ddp_log.js

var monkeyPatches = {
  '_livedata_data': 'DATA',
  '_livedata_error': 'ERROR',
  '_livedata_nosub': 'NOSUB',
  '_livedata_connected': 'CONNECTED',
  '_livedata_result': 'RESULT',
};
_.each(_.keys(monkeyPatches),function(funcName){
  var modifiedFunctionName = funcName+'_original';
  var extension = {};
  extension[modifiedFunctionName] = Meteor.default_connection[funcName];
  _.extend(Meteor.default_connection, extension);

  Meteor.default_connection[funcName] = function(msg){
    console.log(monkeyPatches[funcName]+': ');
    console.log(msg);
    Meteor.default_connection[modifiedFunctionName](msg);
  };
});

var originalSend = Meteor.default_connection._stream.send;
_.extend(Meteor.default_connection._stream,{
  'originalSend': originalSend,
});

Meteor.default_connection._stream.send = function(data) {
  console.log('SENDING: ');
  console.log(JSON.parse(data));
  Meteor.default_connection._stream.originalSend(data);
};

this might prove to be very useful...thank you!