Chapter 24 Socket Interface

Transcription

1 Chapter 24 Socket Interface Sockets Socket System Calls Connectionless Iterative Server UDP Client-Server Programs Connection-Oriented Concurrent Server TCP Client-Server Programs 24-1 Figure 24-1 Data types u_char u_short u_long Unsigned 8-bit character Unsigned 16-bit integer Unsigned 32-bit integer

2 Figure 24-2 Internet address structure s_addr in_addr struct { } ; in_addr u_long s_addr ; 24-3 Figure 24-3 Socket address structure sin_len sin_family sin_port sin_addr sin_zero sockaddr_in... struct { } ; sockaddr_in u_char u_short u_short struct in_addr char sin_len ; sin_family ; sin_port ; sin_addr ; sin_zero [8] ;

3 Figure 24-4 Socket structure Family Type Protocol... sin_len sin_family sin_port sin_addr sin_zero Local Socket Address sin_len sin_family sin_port sin_addr sin_zero Remote Socket Address Socket Figure 24-5 Socket types Application program Stream socket interface TCP Datagram socket interface UDP Raw socket interface IP Physical and data link layers

4 Figure 24-6 Big-endian byte order Data MS byte LS byte Memory A A A A Figure 24-7 Little-endian byte order Data MS byte LS byte Memory A A + 1 A + 2 A

5 Figure 24-8 Byte-order transformation functions Host byte order 16-bit 32-bit htons ntohs htonl ntohl 16-bit 32-bit Network byte order 24-9 Figure 24-9 Declarations for byte-order transformation u_short htons ( u_short host_short ) ; u_short ntohs ( u_short network_short ) ; u_long htonl ( u_long host_long ) ; u_long ntohl ( u_long network_long ) ;

6 Figure Address transformation 32-bit binary address inet_ntoa inet_aton Dotted decimal address Figure Declarations for transformation functions int inet_aton ( const char *strptr, struct in_addr *addrptr ) ; char *inet_ntoa (struct in_addr inaddr ) ;

7 Figure Declaration for byte-manipulation functions void *memset ( void *dest, int chr, int len ) ; void *memcpy ( void *dest, const void *src, int len ) ; int memcmp ( const void *first, const void *second, int len ) ; Figure Declaration for gethostbyname struct hostent *gethostbyname ( const char *hostname ) ;

8 Figure The hostent structure name. alias alias. address address AF_INET 4 h_name h_aliases h_addrtype h_length h_addr_list hostent struct { } ; hostent char *h_name ; char **h_aliases ; int h_addrtype ; int h_length ; char **h_addr_list ; Figure Declaration for socket function int socket (int family, int type, int protocol) ; AF_INET SOCK_DGRAM SOCK_STREAM 0 Returns a socket descriptor if successful; 1 if error

9 Figure Declaration for bind function int bind (int sockfd, const struct sockaddr_in *localaddr, int localaddrlen) ; Returns 0 if successful; 1 if error Figure Declaration for connect function int connect (int sockfd, const struct sockaddr_in *serveraddr, int serveraddrlen) ; Returns 0 if successful; - 1 if error

10 Figure Declaration for listen function int listen (int sockfd, int backlog) ; Returns 0 if successful; - 1 if error Figure Declaration for accept function int accept (int sockfd, const struct sockaddr_in *clientaddr, int *clientaddrlen) ; Returns a socket descriptor if successful; - 1 if error

11 Figure Declaration for sendto function int sendto (int sockfd, const void *buf, int buflen, int flags, const struct sockaddr_in *toaddr, int toaddrlen) ; Returns number of bytes sent if successful; - 1 if error Figure Declaration for recvfrom function int recvfrom (int sockfd, const void *buf, int buflen, int flags const struct sockaddr_in *fromaddr, int *fromaddrlen) ; Returns number of bytes sent if successful; - 1 if error

12 Figure Declaration for read function int read (int sockfd, const void *buf, int buflen ) ; Returns number of bytes read if successful; 0 for end of file; 1 if error Figure Declaration for write function int write (int sockfd, const void *buf, int buflen ) ; Returns number of bytes written if successful; 1 if error

13 Figure Declaration for close function int close (int sockfd ) ; Returns 0 if successful; 1 if error Figure Socket interface for connectionless iterative server Each server serves many clients but handles one request at a time. Requests from different clients can be mingled together. Server Clients socket (...) socket (...) bind (...) Repeat as needed sendto (...) Requests Repeat infinitely recvfrom (...) Process Responses sendto (...) recvfrom (...) close (...)

14 Figure Socket interface for connection-oriented concurrent server Server socket (...) A parent server creates many children; each child server serves only one client. bind (...) listen (...) Client socket (...) connect (...) Connection request Repeat infinitely accept (...) fork (...) close (listening) close (accepting) Repeat as needed Parent server write (...) Repeat as needed request read (...) Process response write (...) read (...) close (...) close (accepting) Child server Figure Client Relationship between the client and the server Server Parent a. After connect, before accept Parent b. After accept Parent Child c. After fork Parent Child d. After parent closes ephemeral port Parent Child e. After child closes well-known port