server.js

var util = Npm.require("util"),
    lastMessage = ''; // The message to return to the user

/**
A custom transport for winston that is used by winston-client to send log messages back to the client
@class MeteorClient
*/
var MeteorClient = Winston.transports.MeteorClient = function (options) {
  this.name = 'meteorClient';
  this.level = options.level || 'silly';
};

util.inherits(MeteorClient, Winston.Transport);

/**
Determine if a dictionary is empty
@method isEmpty
@param {Object} obj The object to test
@return Boolean
*/
function isEmpty(obj) {
  if (Object.keys) { // EMCAScript 5 support
    return Object.keys(obj).length === 0;
  } else { // Old school
    for(var prop in obj) {
        if(obj.hasOwnProperty(prop))
            return false;
    }
    
    return true;
  }
}

MeteorClient.prototype.log = function (level, msg, meta, callback) {
  // @TODO: Make the log message conform better to Winston's own output
  
  lastMessage = level + ': ' + msg;
  if (!isEmpty(meta) && JSON.stringify) {
    lastMessage += '\nmeta = ' + JSON.stringify(meta)
  }
  callback(null, true);
};

Winston.add(Winston.transports.MeteorClient, {});
 
Meteor.methods({
  /**
  A rough equivalent to Winston.log() over Meteor.call.
  Takes the same arguments
  */
  'winston-client.log': function() {
    check(arguments, [Match.Any]);
    Winston.log.apply(null, arguments);
    return lastMessage;
  }
});