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| /**
* petit programme multicast UDP.
* ce programme peut
* soit envoyer un message sur un groupe multicast,
* soit se mettre en écoute du même groupe et afficher les message reçus.
* testé avec cygwin et codegear2009 (c++builder) avec xp et vista.
* *devrait* fonctionner sous VC++ et unixoides.
* si compilé sous Visual / borland, WIN32 doit être défini
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#ifdef WIN32
#include <Winsock2.h>
#include <ws2ipdef.h>
#include <ws2tcpip.h>
#ifdef __BORLANDC__
#pragma link "Ws2_32.lib"
#else
#pragma comment(lib, "Ws2_32.lib")
#endif
#else
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#endif
# define BUFSZ 512
# define MULTICAST_PORT 7766
# define MULTICAST_GROUP "224.0.0.1"
/**
* socket creation function.
* this function will create a multicast socket for reading or writing.
* @param[out] sock: structure sockaddr_in used in recv/sendto functions
* @param[in] type: type of socket: 'r' for reading, 'w' for writing
* @return a opened socket. Exit program on error (exit() called)
*/
int socket_init(struct sockaddr_in *sock, char type)
{
int sd;
unsigned char ttl = 1;
/* create socket */
sd = socket(PF_INET, SOCK_DGRAM, 0);
if (sd < 0) {
perror("socket");
exit(EXIT_FAILURE);
}
/* initialize sock descriptor */
memset(sock, 0, sizeof(struct sockaddr_in));
switch (type) {
/* receive mode */
case 'r':
sock->sin_family = AF_INET;
sock->sin_port = htons(MULTICAST_PORT);
sock->sin_addr.s_addr = htonl(INADDR_ANY);
/* bind */
if (bind(sd, (struct sockaddr *) sock, sizeof(struct sockaddr_in))
< 0) {
perror("bind");
exit(1);
}
/* enable multicast */
{
struct ip_mreq imr;
imr.imr_multiaddr.s_addr = inet_addr(MULTICAST_GROUP); /* multicast group to join */
imr.imr_interface.s_addr = htonl(INADDR_ANY); /* interface to read on */
/* set GROUP option */
if (setsockopt
(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *) &imr,
sizeof(struct ip_mreq)) < 0) {
perror("setsockopt: IP_ADD_MEMBERSHIP");
exit(1);
}
/* enable multicast */
if (0 !=
setsockopt(sd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
sizeof(ttl))) {
perror("setsockopt");
exit(1);
}
}
break;
/* transmission mode */
case 'w':
sock->sin_family = AF_INET;
sock->sin_port = htons(MULTICAST_PORT);
sock->sin_addr.s_addr = inet_addr(MULTICAST_GROUP);
{
/* enable multicast */
if (setsockopt
(sd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
sizeof(ttl)) == -1) {
perror("setsockopt: IP_MULTICAST_TTL");
exit(EXIT_FAILURE);
}
}
break;
default:
printf("socket_init: unknown type /%c/\n", type);
exit(EXIT_FAILURE);
}
return sd;
}
void m_receive(void)
{
struct sockaddr_in from;
socklen_t len = sizeof(from);
/* create the reception socket */
int sd = socket_init(&from, 'r');
int cnt;
char buf[BUFSZ];
/* infinite loop */
while (1) {
/* try to receive from socket */
cnt =
recvfrom(sd, buf, sizeof(buf), 0, (struct sockaddr *) &from,
&len);
if (cnt < 0) {
/* something bad happened, quit */
perror("recvfrom");
exit(1);
} else if (cnt == 0) {
/* socket closed (udp should never goes here) exit while loop */
break;
}
/* all goes right, write the received message */
buf[cnt] = 0;
printf("%s\n", buf);
}
printf("m_receive: done\n");
}
/**
* transmission function.
* @param buf: message to send.
*/
void m_send(const char *buf)
{
struct sockaddr_in to;
int len = sizeof(to);
/* create the transmission socket */
int sd = socket_init(&to, 'w');
int cnt;
/* send the message (just like we whoumd have done with regular
socket */
cnt = sendto(sd, buf, strlen(buf), 0, (struct sockaddr *) &to, len);
if (cnt < 0) {
perror("sendto");
exit(1);
}
}
/** usage :
* cmd.exe r
* cmd.exe w message
*/
void usage(const char *name) {
printf("usage :\n\n");
printf("reception mode\n");
printf("\t %s r\n\n", name);
printf("transmission mode\n");
printf("\t %s w message to send\n", name);
}
/**
* Application entry point
*/
int main(int argc, char **argv)
{
#ifdef WIN32
WSADATA wsaData;
int ret = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (ret != 0) {
printf("WSAStartup failed: %d\n", ret);
return 1;
}
#endif
if (argc < 2) {
usage(*argv);
} else {
switch (*argv[1]) {
case 'r':
/* go in receive mode */
m_receive();
break;
case 'w':
/* note that this method is not optimized : we create a socket
of each word of the message to send. */
{
int i;
for (i = 2; i != argc; ++i) {
/* send each parameter given to program*/
m_send(argv[i]);
}
}
break;
default:
usage(*argv);
}
}
#ifdef WIN32
WSACleanup();
#endif
return 0;
} |
