The basic I/o functions in ANSI C Chapter 2: Socket Programming open: prepare a device or file for input or output Chapter goal: erations close: terminate use of a previously opened device Program interface to read: obtain data from an input device or file, and a Socket API write: transmit data from lication program's nory to an output device Socket programming model Iseek: move to a specific position in a file or device octl: control a device or software used to access it Socket API What is" socke↑"? Originally designed A socket is a virtual connection For BSD UNIX-Berkley Socket Interface between two applications To use with TCP/IP protocols Now Using a socket, two processes can communicate with each other The socket is the major communication Microsoft chose the socket interface as the primary API tool for Internet applications In Ms windows, WINSOCK A socket is bi-directional(full-duplex transmission A socket can be created dynamically Socket as a virtual connection between two processes Specifying a protocol interface Host A o support TCP/IP communicatio (nirmal cowe crion) Information Hiding ge neral ndsuese parameters to make TcP/IP communication The socket interface provides generalized functions that support network communication using many Socket functions refer to all TCP /IP protocols as a (plysical connection)3 哈工大计算机学院 李全龙 Network Application Development Socket Programming 13 The basic I/O functions in ANSI C „ open: prepare a device or file for input or output operations. „ close: terminate use of a previously opened device or file. „ read: obtain data from an input device or file, and place it in the application program’s memory. „ write: transmit data from the application program’s memory to an output device or file. „ lseek: move to a specific position in a file or device. „ ioctl: control a device or software used to access it. 哈工大计算机学院 李全龙 Network Application Development Socket Programming 14 Chapter 2: Socket Programming Chapter goal: „ Program interface to protocol „ Socket API „ Socket programming model 哈工大计算机学院 李全龙 Network Application Development Socket Programming 15 Socket API „ Originally designed „ For BSD UNIX-Berkley Socket Interface „ To use with TCP/IP protocols „ Now „ Industry standard „ Available on many operating systems „ Microsoft chose the socket interface as the primary API. „ In MS Windows, WINSOCK 哈工大计算机学院 李全龙 Network Application Development Socket Programming 16 What is “socket”? • A socket is a virtual connection between two applications • Using a socket, two processes can communicate with each other • The socket is the major communication tool for Internet applications • A socket is bi-directional (full-duplex) transmission • A socket can be created dynamically 哈工大计算机学院 李全龙 Network Application Development Socket Programming 17 Network Socket as a virtual connection between two processes (physical connection) Host B Process 2 Host A Process 1 Network Adapter Card Information Hiding Socket connection (virtual connection) 哈工大计算机学院 李全龙 Network Application Development Socket Programming 18 Specifying a protocol interface „ The designers must choose one of two broad approaches: „ Define functions specifically to support TCP/IP communication. „ Define functions that support network communication in general, and use parameters to make TCP/IP communication in special case. „ The socket interface provides generalized functions that support network communication using many possible protocols. „ Socket functions refer to all TCP/IP protocols as a single protocol family. „ The functions allow the programmer to specify the type of service required rather than the name of a specific protocol