NAD-chapter2.pdf

文档介绍：Chapter 2: Socket Programming
Chapter goal:
„ Program interface to
protocol
„ Socket API
„ Socket programming model
哈工大计算机学院 work Application Development Socket Programming 1
Chapter 2: Socket Programming
Chapter goal:
„ Program interface to
protocol
„ Socket API
„ Socket programming model
哈工大计算机学院 work Application Development Socket Programming 2
Interacting with Protocol
Software
„ Client or server uses transport
protocols
„ Protocol software inside OS
„ Applications outside OS
„ Mechanism needed to bridge the two
„ Called Application Program Interface
(API)
哈工大计算机学院 work Application Development Socket Programming 3
Loosely specified protocol
software interface
„ TCP/IP protocol software is part of the
computer’s system software.
„ TCP/IP was designed to operate in a multi-vendor
environment.
„ TCP/IP does not define details of API
„ The interface between TCP/IP and applications
that use it has been loosely specified.
„ TCP/IP standards do not specify the details of how
application software interfaces with TCP/IP protocol
software
„ They only suggest the required functionality, and allow
system designers to choose the details when creating
an API
哈工大计算机学院 work Application Development Socket Programming 4
Advantages and disadvantages
of Loose specification
„ Advantages:
„ Flexibility and tolerance.
„ Different OS select own implementation.
„ Disadvantages:
„ Designers can make the interface details
different for each OS.
„ Less portable across machines.
„ In practice, only a few APIs have been
developed for use with TCP/IP.
„ Berkeley UNIX: socket interface, or sockets
„ AT&T, System V UNIX: TLI
„ Windows: windows sockets interface, WINSOCK
哈工大计算机学院 work Application Development Socket Programming 5
API functionality
„ API must support:
„ Allocate local resources munication
„ Specify local and munication endpoints
„ Initiate a connection (clien