12.1-Full Stack Java notes: Basic concepts of network programming

What is a computer network?

The distribution of computers in different geographical areas and specialized external equipment with communication lines interconnect into a large, powerful network system, so that many computers can easily transfer information to each other, sharing hardware, software, data information and other resources.

The main functions of computer network:

Resource sharing

Information transmission and centralized processing

Balanced load and distribution processing

Integrated Information Services (www/Integrated Services Digital Network ISDN)

What is network communication protocol ?

There must be some conventions in the Computer Network communication protocol, the rate, transmission code, code structure, transmission Control procedures, error control and other standards.

Network communication interface:

In order for a conversation to be made between two nodes, a communication tool (the interface) must be established between them so that information can be exchanged between each other. The interface consists of two parts:

Hardware Device: Realizes information transmission between nodes.

Software device: A contractual agreement that provides for communication between the parties

Why layering ?

because of the complex connection between nodes, the complex components are decomposed into some simple ingredients, and then compound them up. The most commonly used composite method is the hierarchical way, that is, the same layer can communicate, the previous layer can call the next layer, and the next layer does not occur.

hierarchical provisions of communication protocols :

The user application as the highest level, the physical communication lines as the lowest layer, the process of processing the protocol into several layers, the task of each layer of processing, also stipulates the interface standard of each layer.

1) Physical layers (physical layer)

2) Data Link layer

3) Network Layer Network layer protocol representatives include: IP, IPX, RIP, OSPF, etc.

4) Transport Layer (Transport layer) Transport layer protocol representatives include: TCP, UDP, SPX and so on.

5) NetBIOS (Session layer), ZIP (AppleTalk Area Information Protocol), etc.

6) Presentation layers (Presentation layer) ASCII, ASN.1, JPEG, MPEG, etc.

7) Application tier (application layer) Telnet, FTP, HTTP, SNMP, etc.

Data encapsulation

Data unpacking

IP: IPV4, IPV6

Port:

QQ, MSN, Thunder, Electric Donkey, 360 through the port, you can run multiple network applications on one host. The port is a virtual concept, not that there are really several ports on the host.

Url:

On WWW, each information resource has a unified and unique address, which is called the URL (Uniform Resource Locator), which is the Uniform Resource Locator of www. The URL consists of 4 parts: The protocol, the host domain where the resource resides, the resource file name, and the port number. If the port number is not specified, the protocol default port is used. For example, the default port for the HTTP protocol is 80.

The URL class is provided in the java.net package, which encapsulates a number of complex details that involve obtaining information from a remote site.

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12.1-Full Stack Java notes: Basic concepts of network programming