Socket address structure in <sys/socket.h>:

1
Socket Programming

• Socket address structure in ltsys/socket.hgt
• struct sockaddr
• u_short sa_family / address family AF_xxx
  value /
• char sa_data14 / up to 14 bytes of
  protocol- /
• / specific address /

2
Socket Programming

• Socket address structure in ltnetinet/in.hgt
• (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_zero8 / unused /

4
Socket Programming

• socket specify the type of communication
  protocol desired (TCP, UDP etc.)
• include ltsys/types.hgt
• include ltsys/socket.hgt
• 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 ltsys/types.hgt
• include ltsys/socket.hgt
• int bind(int sockfd, struct sockaddr myaddr,
  int addrlen)
• sockfd socket descriptor (return bymyaddr a
  pointer to a protocol-specific address
• addrlen the size of this address structure
• The output gt 0 if success otherwise, it fails.

7
Socket Programming

• connect establish a connection with a server
• include ltsys/types.hgt
• include ltsys/socket.hgt
• int connect (int sockfd, struct sockaddr
  servaddr, int addrlen)
• same as the system call bind.
• The output gt 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 ltsys/types.hgt
• include ltsys/socket.hgt
• 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 gt 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 ltsys/types.hgt
• include ltsys/socket.hgt
• 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 ltsys/types.hgt
• include ltsys/socket.hgt
• 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 ltsys/types.hgt
• include ltsys/socket.hgt
• 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 ltsys/types.hgt
• include ltnetinet/in.hgt
• 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 ltsys/socket.hgt
• include ltnetinet/in.hgt
• include ltarpa/inet.hgt
• unsigned long inet_addr(char ptr)

14
Socket Programming
Connection-oriented Protocol
Server
Client
15
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))
  lt 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)) lt 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)) lt 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))
  lt 0)
• err_sys(client can't open stream socket)
• if (connect(sockfd, (struct sockaddr )
  serv_addr, sizeof(serv_addr)) lt 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))
  lt 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)) lt 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))
  lt 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)) lt 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)

• define _REENTRANT
• include ltstdio.hgt
• include ltthread.hgt
• define NUM_THREADS 12
• void change_global_data(void ) / for
  thr_create() /
• main(int argc,char argv)
• int i0
• for (i0 ilt 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)

Use online help to find out the information about
thread programming. Try man mutex man
thr_create man thr_join ...