The actual current network model using TCP / IP model, it has been simplified OSI model contains only four layers, from top to bottom is the application layer, transport layer, network layer and link layer (network interface layer), each layer contains a number of agreements.
Protocol (Protocol) network communications is the process of agreement or contract, the parties must comply with in order to communicate properly send and receive data. There are many protocols, such as TCP, UDP, IP, etc., both sides must use the same communication protocol to communicate. Protocol is a specification developed by computer organization, provides a lot of details, such as how to establish a connection, how to recognize each other and so on.
[Protocol is merely a standard, it must be implemented by computer software. For example IP protocol specifies how to find the target computer, then various developers in the development of their own software must comply with the agreement, can not start all over again. ]
TCP / IP model includes TCP, IP, UDP, Telnet, FTP, SMTP, etc. hundreds of interrelated protocols in which TCP and IP are two most commonly used underlying protocol, so they are referred to as the "TCP / IP protocol family. "
socket programming is based on TCP and UDP protocols, their hierarchy as shown below:
