code: public void sendMessage(String pUserName, TextMessage pMessage) throws APPErrorException {
          validOnline(pUserName);
          try {
              mClients.get(pUserName).sendMessage(pMessage);
          } catch (IOException e) {
              throw new APPErrorException("发送消息失败；原因：" + e.getMessage(), e);
          }
      }
docs: 发送信息
  
  @param pUserName
  @param pMessage
  
  @throws APPErrorException