Network Programming basics for UNIX/Linux: Introduction to application layer protocols

Directory

1. HTTP protocol

2. FTP protocol

3. TELNET protocol

4. NFS Protocol

1. HTTP protocol

Application Layer ProtocolHTTP is the core of Web.HTTP is implemented in Web client programs and server programs. client programs and server programs running on different systems communicate with each other by exchanging HTTP messages. The HTTP Protocol defines the data format so that the server and client can communicate data through the Protocol.

The basic content of client-to-Server Communication: Web pages (also known as documents ).

A Web page consists of multiple objects. An object is a file that can be addressable by a URL, such as an HTML file, JPG image, a Java Applet, and a speech clip.

Most Web pages are composed of a basic HTML file and objects referenced in many HTML files. This basic HTML file uses the built-in URL in the file to reference other objects used on this page.

A URL consists of two parts: the server host name that stores the object and the path name of the object. For example, in the following URL:

HTTP is based on the TCP protocol, and its default port is port 80 of the TCP protocol.

Basic HTTP Process:

 

2. FTP protocol

FTP (File Transfer Protocol) is a Protocol for transferring files from one host to another.

The FTP protocol is also based on the TCP protocol.But there is a big difference with the HTTP protocol, the most important thing isThe FTP protocol uses two parallel TCP connections to transmit files. One is the control connection, and the other is the data connection.

Control connectionIt is used to transmit control information between the client and the server (usually called FTP out-of-band data, that is, the control information is not included in the FTP data connection ), for example, user name and password, commands for changing directories, uploading or downloading files, etc.

Data ConnectionUsed to send and receive data.

The FTP protocol works in active and passive modes.The main difference between the two is that the data port processing method is different: the active mode tells the server data connection port after the client connection; the passive mode after the client connection, during data transmission, you can temporarily connect to Port 20 of the FTP server and use this port for data transmission.

FTP transmission mode: ASCII transmission mode and binary transmission mode. The difference between the two lies in whether the data is interpreted. The ASCII mode interprets the data, while the binary mode copies data one by one.

3. Telnet protocol

Telnet is one of the earliest remote logon protocols.You can log on to a remote computer on the local machine using the Telnet protocol.

Remote logon refers to the process in which a user uses telnet commands to temporarily turn his computer into a simulation terminal of the remote host.

For more information about telnet configuration and usage, see http://www.cnblogs.com/nufangrensheng/p/3488122.html.

4. NFS Protocol

NFS is a protocol used for file sharing,It allows file sharing between hosts. The client can operate files on the remote host like files on the local machine.

NFS is a simple protocol that does not provide information transmission protocols and functions. NFS enables data sharing between hosts over the network, because NFS uses some other transmission protocols and mainly uses the Remote Procedure Call function. SoYou must start the RPC service when starting the NFS server..

For more information about NFS server configuration, see http://www.cnblogs.com/nufangrensheng/p/3486839.html.