==============================MODULE40=====================================
|                                                                         |
|  The program examples' source codes have been arranged in the same      |
|  order that appeared in the Tutorial. This is unedited and unverified   |
|  compilation. Published as is basis for educational, reacretional and   |
|  brain teaser purposes. All trademarks, copyrights and IPs, wherever    |
|  exist, are the sole property of their respective owner and/or          |
|  holder. Any damage or loss by using the materials presented in this    |
|  tutorial is USER responsibility. Part or full distribution,            |
|  reproduction and modification is granted to any body.                  |
|     Copyright 2003-2005 © Tenouk, Inc. All rights reserved.		  |
|          Distributed through http://www.tenouk.com			        |
|        		                                                        |
|									                    |
===========================================================================

Compiled using gcc on Linux/Fedora Core 3 machine...

/*****getipaddr.c ******/
/****a hostname lookup program example******/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
struct hostent *h;

/*error check the command line*/
if(argc != 2)
{
fprintf(stderr, "Usage: %s <domain_name>\n", argv[0]);
exit(1);
}

/*get the host info*/
if((h=gethostbyname(argv[1])) == NULL)
{
herror("gethostbyname(): ");
exit(1);
}
else
printf("gethostbyname() is OK.\n");

printf("The host name is: %s\n", h->h_name);
printf("The IP Address is: %s\n", inet_ntoa(*((struct in_addr *)h->h_addr)));
printf("The address length is: %d\n", h->h_length);

printf("Sniffing other names...sniff...sniff...sniff...\n");
int j = 0;
do
{
printf("An alias #%d is: %s\n", j, h->h_aliases[j]);
j++;
}
while(h->h_aliases[j] != NULL);

printf("Sniffing other IPs...sniff....sniff...sniff...\n");
int i = 0;
do
{
printf("Address #%i is: %s\n", i, inet_ntoa(*((struct in_addr *)(h->h_addr_list[i]))));
i++;
}
while(h->h_addr_list[i] != NULL);
return 0;
}

-----------------------------------------------------------------------------------------------

/*serverprog.c - a stream socket server demo*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>

/* the port users will be connecting to */
#define MYPORT 3490
/* how many pending connections queue will hold */
#define BACKLOG 10 

void sigchld_handler(int s)
{
while(wait(NULL) > 0);
}

int main(int argc, char *argv[])
{
/*listen on sock_fd, new connection on new_fd*/
int sockfd, new_fd;
/*my address information*/
struct sockaddr_in my_addr;
/*connector’s address information*/
struct sockaddr_in their_addr;
int sin_size;
struct sigaction sa;
int yes = 1;

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
perror("Server-socket() error lol!");
exit(1);
}
else
printf("Server-socket() sockfd is OK...\n");

if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1)
{
perror("Server-setsockopt() error lol!");
exit(1);
}
else
printf("Server-setsockopt is OK...\n");

/* host byte order*/
my_addr.sin_family = AF_INET;
/* short, network byte order*/
my_addr.sin_port = htons(MYPORT);
/* automatically fill with my IP*/
my_addr.sin_addr.s_addr = INADDR_ANY;

printf("Server-Using %s and port %d...\n", inet_ntoa(my_addr.sin_addr), MYPORT);

/* zero the rest of the struct*/
memset(&(my_addr.sin_zero), '\0', 8);

if(bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1)
{
perror("Server-bind() error");
exit(1);
}
else
printf("Server-bind() is OK...\n");

if(listen(sockfd, BACKLOG) == -1)
{
perror("Server-listen() error");
exit(1);
}
printf("Server-listen() is OK...Listening...\n");

/*clean all the dead processes*/
sa.sa_handler = sigchld_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;

if(sigaction(SIGCHLD, &sa, NULL) == -1)
{
perror("Server-sigaction() error");
exit(1);
}
else
printf("Server-sigaction() is OK...\n");

/*accept() loop*/
while(1)
{
sin_size = sizeof(struct sockaddr_in);
if((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1)
{
perror("Server-accept() error");
continue;
}
else
printf("Server-accept() is OK...\n");
printf("Server-new socket, new_fd is OK...\n");
printf("Server: Got connection from %s\n", inet_ntoa(their_addr.sin_addr));

/* this is the child process */
if(!fork())
{
/* child doesn’t need the listener */
close(sockfd);

if(send(new_fd, "This is a test string from server!\n", 37, 0) == -1)
perror("Server-send() error lol!");
close(new_fd);
exit(0);
}
else
printf("Server-send is OK...!\n");

/* parent doesn’t need this*/
close(new_fd);
printf("Server-new socket, new_fd closed successfully...\n");
}
return 0;
}

-----------------------------------------------------------------------------------------------

/*** clientprog.c ****/
/*** a stream socket client demo ***/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

//the port client will be connecting to
#define PORT 3490
//max number of bytes we can get at once
#define MAXDATASIZE 300

int main(int argc, char *argv[])
{
int sockfd, numbytes;
char buf[MAXDATASIZE];
struct hostent *he;
//connector’s address information
struct sockaddr_in their_addr;

//if no command line argument supplied
if(argc != 2)
{
fprintf(stderr, "Client-Usage: %s the_client_hostname\n", argv[0]);
//just exit
exit(1);
}

//get the host info
if((he=gethostbyname(argv[1])) == NULL)
{
perror("gethostbyname()");
exit(1);
}
else
printf("Client-The remote host is: %s\n", argv[1]);

if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
perror("socket()");
exit(1);
}
else
printf("Client-The socket() sockfd is OK...\n");

//host byte order
their_addr.sin_family = AF_INET;
//short, network byte order
printf("Server-Using %s and port %d...\n", argv[1], PORT);
their_addr.sin_port = htons(PORT);
their_addr.sin_addr = *((struct in_addr *)he->h_addr);
//zero the rest of the struct
memset(&(their_addr.sin_zero), '\0', 8);

if(connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1)
{
perror("connect()");
exit(1);
}
else
printf("Client-The connect() is OK...\n");

if((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
{
perror("recv()");
exit(1);
}
else
printf("Client-The recv() is OK...\n");

buf[numbytes] = '\0';
printf("Client-Received: %s", buf);

printf("Client-Closing sockfd\n");
close(sockfd);
return 0;
}

-----------------------------------------------------------------------------------------------

/*receiverprog.c - a server, datagram sockets*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/* the port users will be connecting to */
#define MYPORT 4950
#define MAXBUFLEN 500

int main(int argc, char *argv[])
{
int sockfd;
/* my address information */
struct sockaddr_in my_addr;
/* connector’s address information */
struct sockaddr_in their_addr;
int addr_len, numbytes;
char buf[MAXBUFLEN];

if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
perror("Server-socket() sockfd error lol!");
exit(1);
}
else
printf("Server-socket() sockfd is OK...\n");

/* host byte order */
my_addr.sin_family = AF_INET;
/* short, network byte order */
my_addr.sin_port = htons(MYPORT);
/* automatically fill with my IP */
my_addr.sin_addr.s_addr = INADDR_ANY;
/* zero the rest of the struct */
memset(&(my_addr.sin_zero), '\0', 8);

if(bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1)
{
perror("Server-bind() error lol!");
exit(1);
}
else
printf("Server-bind() is OK...\n");

addr_len = sizeof(struct sockaddr);

if((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1, 0, (struct sockaddr *)&their_addr, &addr_len)) == -1)
{
perror("Server-recvfrom() error lol!");
/*If something wrong, just exit lol...*/
exit(1);
}
else
{
printf("Server-Waiting and listening...\n");
printf("Server-recvfrom() is OK...\n");
}

printf("Server-Got packet from %s\n", inet_ntoa(their_addr.sin_addr));
printf("Server-Packet is %d bytes long\n", numbytes);
buf[numbytes] = '\0';
printf("Server-Packet contains \"%s\"\n", buf);

if(close(sockfd) != 0)
printf("Server-sockfd closing failed!\n");
else
printf("Server-sockfd successfully closed!\n");
return 0;
}

-----------------------------------------------------------------------------------------------

/*senderprog.c - a client, datagram*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
/* the port users will be connecting to */
#define MYPORT 4950

int main(int argc, char *argv[])
{
int sockfd;
/* connector’s address information */
struct sockaddr_in their_addr;
struct hostent *he;
int numbytes;

if (argc != 3)
{
fprintf(stderr, "Client-Usage: %s <hostname> <message>\n", argv[0]);
exit(1);
}
/* get the host info */
if ((he = gethostbyname(argv[1])) == NULL)
{
perror("Client-gethostbyname() error lol!");
exit(1);
}
else
printf("Client-gethostname() is OK...\n");

if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
perror("Client-socket() error lol!");
exit(1);
}
else
printf("Client-socket() sockfd is OK...\n");

/* host byte order */
their_addr.sin_family = AF_INET;
/* short, network byte order */
printf("Using port: 4950\n");
their_addr.sin_port = htons(MYPORT);
their_addr.sin_addr = *((struct in_addr *)he->h_addr);
/* zero the rest of the struct */
memset(&(their_addr.sin_zero), '\0', 8);

if((numbytes = sendto(sockfd, argv[2], strlen(argv[2]), 0, (struct sockaddr *)&their_addr, sizeof(struct sockaddr))) == -1)
{
perror("Client-sendto() error lol!");
exit(1);
}
else
printf("Client-sendto() is OK...\n");

printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));

if (close(sockfd) != 0)
printf("Client-sockfd closing is failed!\n");
else
printf("Client-sockfd successfully closed!\n");
return 0;
}

-----------------------------------------------------------------------------------------------

/*selectcp.c - a select() demo*/
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
/* file descriptor for standard input */
#define STDIN 0

int main(int argc, char *argv[])
{
struct timeval tval;
fd_set readfds;
tval.tv_sec = 5;
tval.tv_usec = 800000;

FD_ZERO(&readfds);
FD_SET(STDIN, &readfds);
/* don’t care about writefds and exceptfds: */
select(STDIN+1, &readfds, NULL, NULL, &tval);
if (FD_ISSET(STDIN, &readfds))
  printf("A key was pressed lor!\n");
else
  printf("Timed out lor!...\n");
return 0;
}

=====================================================================================================