ninth week

This week's learning summary:

 

Knowledge point

Network model:
1. OSI reference model
2. TCP/IP reference model
Network communication elements:

1. IP address
2. The port number
3. Just think about the transmission protocol
   , if you want to communicate with Zhang San, the first thing you need to do is to find the host of Zhang San, then how to find it, and what method to complete the communication between the two machines?
   Steps: 1) Find the IP of the other party
   2) The data is to be sent to the application designated by the other party. In order to identify these applications, these network applications are identified with numbers. For the convenience of calling this number, it is called the port.
   Note: The ports here are not actual ports on the physical machine, but logical ports.
   3) Define a communication rule. This communication rule is called a protocol.
   International organizations have defined a common protocol--TCP/IP protocol.
   Port number:
   Features:
   The logical address used to identify the process.
   Valid port numbers: 0—65535, of which 0—1024 are used or reserved ports by the system.
   Transport Protocol: The rules of communication.
   Common protocols: TCP, UDP.
   The difference between TCP and UDP:
   UDP: 1) Encapsulates data, source and destination into data packets without establishing a connection.
   2) The size of each data packet should be limited to 64k
   3) Because there is no connection, it is an unreliable protocol.
   4) No need to establish connection, fast speed.

4. , UDP datagram: The basic mode of communication based on UDP is:

5. Data is packaged, called a packet (like a letter is put into an envelope), and the packet is sent to its destination.
6. Accept packets from others (like receiving envelopes), and then look at the contents of the packets.
7. Send packets.