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Socket Programming

Socket Programming. Socket address structure in <sys/socket.h>: struct sockaddr{ u_short sa_family; /* address family: AF_xxx value */ char sa_data[14]; /* up to 14 bytes of protocol- */ /* specific address */ }. Socket Programming. Socket address structure in <netinet/in.h>:

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Socket Programming

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  1. Socket Programming • Socket address structure in <sys/socket.h>: struct sockaddr{ u_short sa_family; /* address family: AF_xxx value */ char sa_data[14]; /* up to 14 bytes of protocol- */ /* specific address */ }

  2. Socket Programming • Socket address structure in <netinet/in.h>: (Internet family) struct in_addr{ u_long s_addr; /* 32-bit netid/hostid */ /* network byte ordered */ }

  3. Socket Programming struct sockaddr_in{ short sin_family; /* AF_INET */ u_short sin_port; /* 16-bit port number */ /* network byte ordered */ struct in_addr sin_addr; /* 32-bit netid/hostid */ /* network byte ordered */ char sin_zero[8]; /* unused */ }

  4. Socket Programming • socket : specify the type of communication protocol desired (TCP, UDP etc.) #include <sys/types.h> #include <sys/socket.h> int socket(int family, int type, int protocol); family: AF_UNIX (UNIX internal protocol) AF_INET (Internet protocols) AF_NS (Xerox NS protocols) AF_IMPLINK (IMP link layer) (AF: address family)

  5. Socket Programming type: SOCK_STREAM (stream socket, TCP) SOCK_DGRAM (datagram socket, UDP) SOCK_RAW (raw socket) SOCK_SEQPACKET (sequenced packet socket) SOCK_RDM (reliably delivered message socket) (not implemented yet) protocol: typically set to 0 for most user applications The output of the system call is the socket descriptor.

  6. Socket Programming • bind: assign a name to an unnamed socket #include <sys/types.h> #include <sys/socket.h> int bind(int sockfd, struct sockaddr *myaddr, int addrlen); sockfd: socket descriptor (return by*myaddr: a pointer to a protocol-specific address addrlen: the size of this address structure The output > 0 if success; otherwise, it fails.

  7. Socket Programming • connect: establish a connection with a server #include <sys/types.h> #include <sys/socket.h> int connect (int sockfd, struct sockaddr *servaddr, int addrlen); same as the system call bind. The output > 0 if success; otherwise, it fails.

  8. Socket Programming • listen: is used by a connection-oriented server to indicate that it is willing to receive connections #include <sys/types.h> #include <sys/socket.h> int listen (int sockfd, struct backlog); backlog: specify how many connection requests can be queued by the system while it waits for the server to execute the accept system call (default as 5). The output > 0 if success; otherwise, it fails.

  9. Socket Programming • accept: take the first connection request on the queue and create another socket with the same properties as sockfd. #include <sys/types.h> #include <sys/socket.h> int accept (int sockfd, struct sockaddr *peer, int *addrlen); peer: the address of connected peer process (the client). addrlen: the size of peer. The output of the system call is the socket descriptor.

  10. Socket Programming • send, sendto, recv and recvform #include <sys/types.h> #include <sys/socket.h> int send(int sockfd, char *buff, int nbytes, int flags); int sendto(int sockfd, char *buff, int nbytes, int flags, struct sockaddr *to, int addrlen); int recv(int sockfd, char *buff, int nbytes, int flags); int recvfrom(int sockfd, char *buff, int nbytes, int flags, struct sockaddr *to, int addrlen); flag: usually zero

  11. Socket Programming • close: close a socket #include <sys/types.h> #include <sys/socket.h> int close (int fd); • bzero: writes the specified number of null bytes to the specified destination. bzero(char *dest, int nbytes);

  12. Socket Programming • htonl: convert host-to-network to long integer • htons: convert host-to-network to short integer #include <sys/types.h> #include <netinet/in.h> u_long htonl(u_long hostlong); u_short htons(u_long hostshort);

  13. Socket Programming • inet_addr: convert a character string in dotted-decimal notation to a 32-bit Internet address #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> unsigned long inet_addr(char *ptr);

  14. connect ( ) socket ( ) socket ( ) bind ( ) listen ( ) connection establishment accept ( ) blocks until connection from client data (request) write ( ) read ( ) process request data (reply) write ( ) read ( ) Socket Programming Connection-oriented Protocol Server Client

  15. bind ( ) socket ( ) socket ( ) bind ( ) recvfrom ( ) blocks until data received from a client data (request) sendto ( ) process request data (reply) sendto ( ) recvfrom ( ) Socket Programming Connectionless Protocol Server Client

  16. Socket Programming int tcp_serv() /* server program: setup a TCP connection */ { int sockfd, newsockfd, clilen; struct sockaddr_in cli_addr, serv_addr; if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) < 0) err_dump(“server: can't open stream socket”); bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); /* INADDR_ANY: any Internet interface on the system */

  17. Socket Programming serv_addr.sin_port = htons(SERV_TCP_PORT); if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) err_dump(“server: can't bind local address”); listen(socfd, 5); clilen = sizeof(cli_addr); if ((newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen)) < 0) err_dump(“server: accept error”); }

  18. Socket Programming int tcp_client() /* client program: setup a TCP connection */ { int sockfd, newsockfd, clilen; struct sockaddr_in serv_addr; bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = inet_addr(SERV_HOST_ADDR); serv_addr.sin_port = htons(SERV_TCP_PORT);

  19. Socket Programming if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) < 0) err_sys(“client: can't open stream socket”); if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) err_sys(“client: can't bind local address”); /* do the transmission */ close(sockfd); }

  20. Socket Programming tcp_send(s_act, msg_ptr, msg_len) /* ipc_send: send data message “msg” within stream domain */ int s_act; /* actual socket descriptor of connection */ char *msg_ptr; /* pointer to data msg unit */ int msg_len; /* length of data msg unit */ { int cc = 0, rc; cc = send(s_act, msg_ptr, msg_len, 0); /*UNIX system call */ if (cc == -1) {perror("send: ! "); rc = cc; } /* error report */ else rc = OK (=1); return (rc); }

  21. Socket Programming tcp_receive(s_act, buf_ptr, buf_len) /* receive data within UNIX*/ int s_act; /* socket descriptor of ipc connection */ union u_du *buf_ptr; /* pointer to message buffer */ int *buf_len; /* length of message buffer */ { int cc, rc; cc = recv(s_act, buf_ptr, *buf_len, 0); /* UNIX syst call */ if (cc == -1) { perror("recv: "); rc = cc; } else {*buf_len = cc; rc = OK (= 1); } return (rc); }

  22. Socket Programming int udp_serv() /* server program: setup a UDP connection */ { int sockfd, newsockfd, clilen; struct sockaddr_in cli_addr, serv_addr; if ((sockfd = socket (AF_INET, SOCK_DGRAM, 0)) < 0) err_dump(“server: can't open datagram socket”); bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); /* INADDR_ANY: any Internet interface on the system */

  23. Socket Programming serv_addr.sin_port = htons(SERV_UDP_PORT); if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) err_dump(“server: can't bind local address”); /* do the transmission */ }

  24. Socket Programming int udp_client() /* client program: setup a UDP connection */ { int sockfd, newsockfd, clilen; struct sockaddr_in cli_addr, serv_addr; bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = inet_addr(SERV_HOST_ADDR); serv_addr.sin_port = htons(SERV_UDP_PORT); if ((sockfd = socket (AF_INET, SOCK_DGRAM, 0)) < 0) err_dump(“client: can't open datagram socket”);

  25. Socket Programming bzero((char *) &cli_addr, sizeof(cli_addr)); cli_addr.sin_family = AF_INET; cli_addr.sin_addr.s_addr = htonl(INADDR_ANY); cli_addr.sin_port = htons(0); if (bind(sockfd, (struct sockaddr *) &cli_addr, sizeof(cli_addr)) < 0) err_dump(“client: can't bind local address”); /* do the transmission */ close(sockfd); }

  26. Socket Programming udp_send( msg_ptr, msg_len, addr_ptr, addr_len ) char *msg_ptr; /* pointer to message */ int msg_len; /* length of message */ struct sockaddr_in *addr_ptr; /* socket address */ int addr_len; /* length of socket address */ { int cc; addr_ptr.sin_addr.s_addr = htonl(st_addr); /*convert address*/ cc = sendto(s_udp, msg_ptr, msg_len, 0 addr_ptr, addr_len ); if (cc == -1) {perror("sendto: "); return(cc);} else return(OK); }

  27. Socket Programming udp_receive(msg_ptr, msg_len, addr_ptr, addr_len) char *msg_ptr; /* pointer to message “msg” */ int msg_len; /* length of message */ struct sockaddr_in *addr_ptr; /* socket address */ int addr_len; /* length of socket address */ { int cc; cc = recvfrom(s_udp, msg_ptr, *msg_len, 0, addr_ptr, addr_len ); if (cc == -1) {perror("recvfrom: "); return(cc); } else return(OK); }

  28. Thread Programming (Try the program) Use online help to find out the information about thread programming. Try: man mutex man thr_create man thr_join …... • #define _REENTRANT • #include <stdio.h> • #include <thread.h> • #define NUM_THREADS 12 • void *change_global_data(void *); /* for thr_create() */ • main(int argc,char * argv[]) { • int i=0; • for (i=0; i< NUM_THREADS; i++) { • thr_create(NULL, 0, change_global_data, NULL, 0, NULL); • } • while ((thr_join(NULL, NULL, NULL) == 0)); • } • void * change_global_data(void *null) { • static mutex_t Global_mutex; • static int Global_data = 0; • mutex_lock(&Global_mutex); • Global_data++; • sleep(1); • printf("%d is global data\n",Global_data); • mutex_unlock(&Global_mutex); • return NULL; • }

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