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計算機遠程通信和遠程控制_外文翻譯

一、以數據庫為中心的監控方案

傳統的監控方法基本上都是以數據庫為中心的解決方案,其中的控制網絡可以是各種現場總線,也可以是其它工業控制網絡,各個控制節點通過它進行通訊,監控機通過發射電臺對電源運行狀況進行監測,收集現場信息,經處理后傳送給實時數據庫服務器;Web服務器根據客戶端瀏覽器發來的HTTP請求,通過服務器擴展模塊,從實時數據庫中獲取數據,然后傳回給客戶端瀏覽器進行顯示?梢钥闯,整個過程都是圍繞著實時數據庫服務器展開的。這種方法在實際應用中存在許多不足。例如,相對于監測功能,控制功能的實現比較困難,編程上難度較大,特別是安全性方面如認證、加密。為解決實時性問題,一般采用輪詢方式,由客戶瀏覽器定時刷新網頁,而這會導致效率低下,有些系統也采用事件觸發方式,利用數據庫服務器的觸發器功能主動推(push)數據,但它一般要求Web服務器與數據庫服務器位于同一臺機器上,不便于系統擴展; 數據庫服務器是整個系統的核心,需處理Web服務器與監控機的請求,工作負載很重,有可能成為系統性能瓶頸。這些不足之處隨著應用模型的擴大顯得越來越明顯,需要新的解決方案。

1.1服務器方面

1.打開一通信通道并告知本地主機,它愿意在某一公認地址上接收客戶請求;

2. 等待客戶請求到達該端口;

3. 接收到重復服務請求,處理該請求并發送應答信號。接收到并發服務請求,要激活一新進程來處理這個客戶請求。新進程處理此客戶請求,并不需要對其它請求作出應答。服務完成后,關閉此新進程與客戶的通信鏈路,并終止。

4. 返回第二步,等待另一客戶請求;

5.關閉服務器。

1.2客戶方面

1.打開一通信通道,并連接到服務器所在主機的特定端口;

2.向服務器發送服務請求報文,等待并接收應答;繼續提出請求;

3.請求結束后關閉通信通道并終止。

從上面所描述過程可知:

1.客戶與服務器進程的作用是非對稱的,因此編碼不同。

2.服務進程一般是先于客戶請求而啟動的。只要系統運行,該服務進程一直存在,直到正;驈娖冉K止。面向連接的基于Socket的客戶機/服務器結構應用程序的基本流程如圖

 一下是英文部分譯文

 

Database-centred programme to control

Traditional control methods are basically a database-centred solutions, which can be controlled network of ground radar, and can also be other industrial control network, the control node through its communication, surveillance plane fired by radio to power performance monitoring, collection site information processed immediately after transmission to the database server; Web server devices based on customer-made to the web browser request through server extension modules from real-time databases, and then sent back to the client side browser for show. We can see that the whole process is around real-time database server started. Practical application of this method in the presence of many inadequacies. For example, in relation to the monitoring functions, control functions to achieve more difficult, it is quite difficult programming, and in particular the safety aspects such as authentication, encryption. To address immediate issues, the general polling methods used by the client browser regularly updated website, which would lead to inefficiency, and some also use the system to trigger events, the use of the database server to push functional capability (computer) data, but it generally requires Web server devices and database servers located in the same machine. not easy system expansion; database server is the core of the system as a whole, to deal with Web server devices and surveillance aircraft request, heavy work load, the system may become performance bottlenecks. With these deficiencies in the application of models to become increasingly evident that the need for new solutions.

以上是一部分介紹,如需要完整的資料或者如不符合您的要求,請聯系技術人員qq:1587620172咨詢 微信:phpvisa66

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