Java Network Programming Notes (1)

Java Network Programming notes
N5
1. Basic network concepts
Chapter2 Basic Network Concepts
2.1 Networks
Keywords: network, node, host, address, name, packet-switched, protocol
A network is a collection of computers and other devices that can send and receive data in more or less real time.
Each machine on the network is called a node. Most nodes are computers, but printers, routers, bridges, gateways, dumb terminals, and happy machines can all be nodes, but you usually only talk to other computers.
A fully functional computer node is called a host ).
Each network node has an address that uniquely identifies a series of bytes. The method for allocating addresses in different networks is the same. The Ethernet address is attached to the physical Ethernet hardware. The device manufacturer must ensure that the addresses of these hardware are unique. The Internet address of a computer is usually allocated by the organization responsible for the address allocation. The addresses that can be allocated to these organizations are provided by the ISP (Internet Service Provider) of the organization. ISP obtains an IP address (Internet Protocol address) from one of the three regional Internet registrars ). For example, the American Registry for Internet Numbers is registered in America and Africa ). The IP address of the registry is Assigned by IANA (Internet Assigned Numbers Authority.
In some types of networks, nodes can use human-readable names. The corresponding name and address are not unchanged. The name can be changed, and the address can be changed. The name can be changed. A single address can usually have multiple names, and a single name can also correspond to multiple addresses (although this is rare)
All modern computer networks are packet-switched networks. Data transmitted over the network is divided into packages, and each package is processed independently. Each package contains "who sent me" and "where I am going. The biggest advantage of packet switching is that many switches can be performed at the same time, and several computers can share a cable.
Protocol is a set of precise rules that define how computers communicate, including address format and data subcontracting. A publicly published protocol allows software and devices from different vendors to communicate with each other. For example, the web browser does not need to care about whether the server is a Unix workstation, Windows box, or Mac machine, because both the server and the browser use the same platform-independent http protocol to talk.
2.2 The Layers of a Network
Standard TCP/IP layer-4 model:
Application Layer
Transport Layer (TCP, UDP)
InternetLayer (IP)
The Host-To-Network Layer (Ethernet, LocalTalk, FDDI ...)
90% of Java Network programming is at the application layer and only needs to talk with the transport layer. The remaining 10% is on the transmission layer, which is used to communicate with the application layer and the inter-network layer.
The application layer seems to be directly talking to the application layer of other hosts, and the network creates a logical link between the two application layers.