Bitex.prototype.requestOrderList = function(opt_requestId, opt_page, opt_limit, opt_filter){
    var self = this
      , reqId = opt_requestId || parseInt( 1e7 * Math.random() , 10 )
      , page = opt_page || 0
      , limit = opt_limit || 10
      , msg = {
        'MsgType': 'U4',
        'OrdersReqID': reqId,
        'Page': page,
        'PageSize': limit,
        'Filter': ["has_leaves_qty eq 1"]
    };

    if (typeof opt_filter !== 'undefined') {
        msg['Filter'] = opt_filter;
    }

    self.ws.send(JSON.stringify(msg));

    return reqId;
}