We have already described client/server computing and the revolution in computing architecture brought about by client/server computing. You already know that a server is a computer attached to a network that stores files, controls peripheral devices, interfaces with the outside world—including the Internet—and does some processing for other computers on the network.

　　我们已经描述了客户机/服务器计算技术及其在计算机技术结构中引起的革命。你已经知道服务器是一台联接到网络的计算机，用于储存文件、控制外设、与外界——包括因特网接口，且为网络上的其他计算机进行一些处理。

　　But what is a Web server? Web server software refers to the software that enables a computer to deliver Web pages written in HTML to client machines on a network that request this service by sending an HTTP request. The two leading brands of Web server software are Apache, which is free Web server shareware that accounts for about 60% of the market, and Microsoft’s NT Server software, which accounts for about 20% of the market.

　　但什么是网络服务器？网络服务器软件是一种使计算机能够向网上客户机传递HTML网页的软件，而客户机通过发出HTTP请求申请这种服务。网络服务器软件的两种主要品牌是Apache和微软的NT服务器软件,前者是一种免费的网络服务器共享软件，约占有60%的市场；后者约占有20%的市场。

　　Aside from responding to requests for Web pages, all Web servers provide some additional basic capabilities such as the following:

　　File Transfer Protocol (FTP)—This protocol allows users to transfer files to and from the server. Some sites limit file uploads to the Web server, while others restrict downloads, depending on the user’s identity.

　　除了回应网页请求之外，所有的网络服务器还提供一些附加的基本能力，例如下列各项:

　　文件传输协议(FTP)——这个协议允许使用者从服务器来回移动文件。根据使用者的身份不同，一些网站限制文件上传到网络服务器,而其他网站限制下载。

　　Security services—These consist mainly of authentication services that verify that the person trying to access the site is authorized to do so. For Web sites that process payment transactions, the Web server also supports Secure Sockets Layer (SSL), the Internet protocol for transmitting and receiving information securely over the Internet. When private information such as names, phone numbers, addresses, and credit card data need to be provided to a Web site, the Web server uses SSL to ensure that the data passing back and forth from the browser to the server is not compromised.

　　安全服务——主要由认证服务组成，确认人们试图对网站进行的访问是经过授权的。对于处理支付交易的网站，网络服务器也支持加密套接字协议层(SSL)——用于在因特网上安全地传输与接收信息的因特网协议。当私人信息如姓名、电话号码、地址和信用卡数据等需要向一个网站提供时，网络服务器使用SSL确保从浏览器到服务器来回传递的数据不被损害。

　　Search engine—Just as search engine sites enable users to search the entire Web for particular documents, search engine modules within the basic Web server software package enable indexing of the site’s Web pages and content, and permit easy keyword searching of the site’s content. When conducting a search, a search engine makes use of an index, which is a list of all the documents on the server. The search term is compared to the index to identify likely matches.

　　搜索引擎——正如搜索引擎网站使用户能够为特殊的文件搜寻整个万维网,基本网络服务器软件包中的搜寻引擎模块允许对网站的网页和内容进行索引,并允许网站内容的关键词搜索。当进行搜寻时,搜索引擎使用索引, 索引是服务器上所有文件的列表。将搜寻项与索引进行比较，确定可能的匹配。

　　Data capture—Web servers are also helpful at monitoring site traffic, capturing information on who has visited a site, how long the user stayed there, the date and time of each visit, and which specific pages on the server were accessed. This information is compiled and saved in a log file, which can then be analyzed by a user log file. By analyzing a log file, a site manager can find out the total number of visitors, average length of each visit, and the most popular destinations, or Web pages.

　　数据捕获——网络服务器还有助于监测网站访问量，捕获有关谁访问某个网站、用户在那里停留多久、每次访问的日期和时间、和服务器上哪个特定网页被存取等信息。这个信息被汇编并保存在一个日志文件中,然后能通过用户日志文件进行分析。通过分析一个日志文件，网站管理员能找出访客总数、平均访问时间长度和最流行的目的地或网页。