code: function(name, service) {
    this.name = name;
    this.groups = {};       // group map for uids. key: sid, value: [uid]
    this.records = {};      // member records. key: uid
    this.__channelService__ = service;
    this.state = ST_INITED;
    this.userAmount =0;
  }
docs: Channel maintains the receiver collection for a subject. You can
  add users into a channel and then broadcast message to them by channel.
  
  @class channel
  @constructor