计算机网络实验七Socket Programming.pptxVIP

Lab7 Socket Programming Application Programming InterfaceInterface exported by the networkSince most network protocols are implemented (those in the high protocol stack) in software and nearly all computer systems implement their network protocols as part of the operating system, when we refer to the interface “exported by the network”, we are generally referring to the interface that the OS provides to its networking subsystemThe interface is called the network Application Programming Interface (API) Application Programming Interface (Sockets)Socket Interface was originally provided by the Berkeley distribution of Unix- Now supported in virtually all operating systemsEach protocol provides a certain set of services, and the API provides a syntax by which those services can be invoked in this particular OS SocketWhat is a socket?The point where a local application process attaches to the networkAn interface between an application and the networkAn application creates the socket The interface defines operations forCreating a socketAttaching a socket to the networkSending and receiving messages through the socketClosing the socket SocketSocket FamilyPF_INET denotes the Internet family PF_UNIX denotes the Unix pipe facility PF_PACKET denotes direct access to the network interface (i.e., it bypasses the TCP/IP protocol stack)Socket TypeSOCK_STREAM is used to denote a byte streamSOCK_DGRAM is an alternative that denotes a message oriented service, such as that provided by UDP Creating a Socketint sockfd = socket(address_family, type, protocol);The socket number returned is the socket descriptor for the newly created socketint sockfd = socket (PF_INET, SOCK_STREAM, 0);int sockfd = socket (PF_INET, SOCK_DGRAM, 0); The combination of PF_INET and SOCK_STREAM implies TCP Client-Serve Model with TCPServerPassive openPrepares to accept connection, does not actually establish a connectionServer invokes int bind (int socket, struct sockaddr *address, int addr_len) int listen (int