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This article is to share with you about how to analyze FTP server and Web server. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

A server, also known as a server, is a device that provides computing services. Because the server needs to respond to the service request and process it, generally speaking, the server should have the ability to undertake and guarantee the service.

The composition of the server includes processors, buses, etc., which is similar to the general architecture, but it requires high reliability, scalability, manageability and other aspects because of the need to provide highly reliable services.

In the network environment, according to the different types of services provided by the server, it is divided into file server, web server and so on.

1. Ftp server

FTP servers (File Transfer Protocol Server) are computers that provide file and access services on the Internet. FTP is File Transfer Protocol (File transfer Protocol). As the name implies, it is a protocol specifically used to transfer files. To put it simply, the server that supports the FTP protocol is the FTP server. Generally speaking. The primary purpose of users is to achieve, which is one of the very important contents of information sharing. Like most, FTP is one. The user connects to the remote FTP server program through a program that supports the FTP protocol. The user issues a command to the server program through the program, and the server program executes the command issued by the user and returns the result of the execution to. For example, a user issues a command that requires the server to send a copy of a file to the user, and the server responds to this command by sending the specified file to the user's machine. The program receives the file on behalf of the user and stores it in the user directory.

FTP is a TCP-only service and does not support UDP. What is different is that FTP uses two ports, a data port and a command port (also known as a control port). Generally speaking, these two ports are 21 (command port) and 20 (data port). But the way FTP works, the data port is not always 20. This is the difference between active and passive FTP. There are two main modes of operation:

1. Active ftp

In Port mode, the client connects from an arbitrary unprivileged port N (N > 1024) to the command port of the FTP server, that is, port 21. And then the client starts

Listen on port Numb1 and send the FTP command "port Number1" to the FTP server. The server then connects from its own data port (20) to the data port specified by the client (Number1).

For the firewall in front of the FTP server, the following traffic must be allowed to support active FTP:

(1) any port greater than 1024 to port 21 of the FTP server. (client initialized connection)

(2) Port 21 of the FTP server to a port greater than 1024. (the server responds to the client's control port)

(3) Port 20 of the FTP server to ports greater than 1024. (the server initializes the data connection to the data port of the client)

(4) Port 20 greater than 1024 to the FTP server (the client sends the ACK response to the server's data port)

2. Passive ftp

In order to solve the problem of the connection initiated by the server to the customer, a different way of FTP connection has been developed. This is called passive mode, or PASV, which is enabled when the client informs the server that it is in passive mode.

In passive FTP, both command connection and data connection are initiated by the client, which can solve the problem that the incoming connection from the data port from the server to the client is filtered out by the firewall.

When a FTP connection is opened, the client opens two arbitrary unprivileged local ports (N > 1024 and Number1). * Ports connect to port 21 of the server, but unlike active FTP, the client does not submit PORT commands and allows the server to connect to its data port back and forth, but to submit PASV commands. The result is that the server opens an arbitrary unprivileged port (P > 1024) and sends a PORT P command to the client. The client then initiates a connection from local port Number1 to port P of the server to transmit data.

For server-side firewalls, the following communication must be allowed to support passive FTP:

(1) Port 21 from any port greater than 1024 to the server (client initialized connection)

(2) Port 21 of the server to any port greater than 1024 (the server responds to the connection to the control port of the client)

(3) from any port greater than 1024 to the greater than 1024 port of the server (client initialization data connects to any port specified by the server)

(4) from the server's port greater than 1024 to the remote port greater than 1024 (the server sends ACK responses and data to the client's data port)

II. Web server

Web server generally refers to a certain type of server that resides on the Internet and can provide documents to the Web. You can place website files for the world to browse, and you can place data files for the world to download. Currently, the three most mainstream Web servers are Apache Nginx IIS.

As a Web server, the first thing is to ensure uninterruptible power supply, and the computer room should control the relative temperature and humidity. There are additional UPS Uninterruptible Power supplies and regulators, and this Web server hardware configuration can outperform basic WEB request services, such as massive data exchange, file reading and writing, and may have bandwidth bottlenecks.

Contents of the Web server

The ⑴ application layer uses the HTTP protocol.

⑵ HTML document format.

⑶ browser uniform Resource Locator (URL).

1. Introduction to WWW

WWW is the abbreviation of World Wide Web (World wide Web). It can also be abbreviated as Web. The Chinese name is "World wide Web". It originated from the master-slave distributed hypermedia system developed by the European Quantum Physics Laboratory CERN (the European Laboratory for Particle Physics) in March 1989. Through the World wide Web, people can quickly and easily obtain rich information by using simple methods. Because users no longer need to pay attention to some technical details in the process of accessing information resources through Web browsers, and the interface is very friendly, Web has been warmly welcomed as soon as it was launched on Internet, became popular all over the world, and developed explosively rapidly.

2. The development and characteristics of WWW.

For a long time, people only get information through traditional media, such as television, newspapers, magazines and radio. However, with the development of computer network, people who want to obtain information are no longer satisfied with the unilateral transmission and acquisition of traditional media, but want to have a subjective choice. Now, various categories are available on the network, such as literature periodicals, industry information, meteorological information, paper retrieval and so on. Due to the development of computer network, the acquisition of information has become very timely, rapid and convenient.

In 1993, the technology of WWW made a breakthrough. It solved the problems of text display, data connection and image transmission in remote information services, and made WWW the most popular way of information transmission on Internet. Today, Web servers have become a cluster of computers on Internet, with so many Web documents and a wide range of linked networks that it is hard to imagine. It can be said that Web has taken a groundbreaking step for the popularity of Internet and is the most exciting achievement on Internet in recent years.

WWW adopts browser / server structure, and its function is to organize and store all kinds of WWW resources, and respond to the request of client software, transfer the resources needed by customers to Windows 95 (or Windows98), Windows NT, UN Ⅸ or Linux and other platforms.

There are two most frequently used web server server software: the Information Server (iis), and Apache.

Generally speaking, Web server serves pages enable browsing by browsers, while the server provides methods (methods) that client applications can call. Specifically, you can say that the Web server specializes in processing HTTP requests (request), but the application server provides (serves) business logic (business logic) to the application through many protocols.

Web server can parse (handles) the HTTP protocol. When the Web server receives a HTTP request (request), it returns a HTTP response (response), such as a HTML page. In order to process a request (request), the Web server can response a static page or image, perform a page jump (redirect), or delegate the generation of a dynamic response (dynamic response) to some other program such as CGI script, JSP (JavaServer Pages) script, servlets,ASP (Active Server Pages) script, server-side JavaScript, or some other server-side (server-side) technology. Regardless of their purpose, these server-side-side programs usually generate a HTML response for browsers to browse.

You know, the proxy model (delegation model) of the Web server is very simple. When a request is sent to the Web server, it simply passes the request (request) to the program that can handle the request (request) well. The Web server only provides an environment that can execute server-side (server-side) programs and return response (response) generated by the program, without going beyond the scope of its functions. Server-side (server-side) programs usually have the functions of transaction processing (transaction processing), database connection (database connectivity) and message (messaging).

Although the Web server does not support transaction processing or database connection pooling, it can configure (employ) various strategies (strategies) to achieve fault tolerance (fault tolerance) and scalability (scalability), such as load balancing (load balancing) and buffering (caching). Cluster characteristics (clustering-features) are often mistaken for only application server-specific features.

The above is how to analyze the FTP server and Web server. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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