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>:(Internet family)

struct in_addr{u_long s_addr; /* 32-bit netid/hostid */

/* network byte ordered */}

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 */}

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)

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.

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 addressaddrlen: the size of this address structure

The output > 0 if success; otherwise, it fails.

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.

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.

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.

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

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);

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);

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);

Socket Programming

read ( )

connect ( )

socket ( )

write ( )

socket ( )

bind ( )

listen ( )

read ( )

accept ( )

write ( )

blocks until connection from client

process request

connection establishment

data (request)

data (reply)

Connection-oriented Protocol

Server

Client

Socket Programming

ConnectionlessProtocol

Server

Client

recvfrom ( )

bind ( )

socket ( )

sendto ( )data (request)

data (reply)

socket ( )

bind ( )

recvfrom ( )

sendto ( )

blocks until data received from a client

process request

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 */

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”);}

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);

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);}

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);}

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);

}

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 */

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 */}

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”);

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);}

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);}

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);}

Socket Programming

#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; }

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

…...