A client and server
Client: Client (Client), also known as the client, refer to the corresponding server, providing customers with local service program. In addition to some applications run only locally, general
Mounted on a common client, we need co-ordination with the server.
Server: server for client services, content services, such as providing resources to the client, the client saved data.
Two .Http agreement
Application layer protocol
Three .URL resolve
It contains the protocol, domain name, port, virtual directory, parameters.