listen.c

使用三块无线网卡在两个嵌入式板子

/*   * listen.c - An IP multicast client */
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdlib.h>
#include <unistd.h>
char * host_name = "224.0.0.1";  /* 多播IP地址 */
int port = 6789;
int main ( void )
{

	struct ip_mreq command;
	int loop = 1;  /* 多播循环 */
	int iter = 0;
	int sin_len;
	char message[256];
	int socket_descriptor;

	struct sockaddr_in sin;

	struct hostent *server_host_name;

	if ( ( server_host_name = gethostbyname ( host_name ) ) == 0 )
	{
		perror ( "gethostbyname" );
		exit ( EXIT_FAILURE );
	}     /*bzero(&sin, sizeof(sin));*/

	memset ( &sin, 0, sizeof ( sin ) );

	sin.sin_family = AF_INET;

	sin.sin_addr.s_addr = htonl ( INADDR_ANY );

	sin.sin_port = htons ( port );

	if ( ( socket_descriptor = socket ( PF_INET, SOCK_DGRAM, 0 ) ) == -1 )
	{
		perror ( "socket" );
		exit ( EXIT_FAILURE );
	}  /* 调用bind之前，设置套接口选项启用多播IP支持*/

	loop = 1;

	if ( setsockopt ( socket_descriptor,  SOL_SOCKET, SO_REUSEADDR,  &loop, sizeof ( loop ) ) < 0 )
	{
		perror ( "setsockopt:SO_REUSEADDR" );
		exit ( EXIT_FAILURE );
	}

	if ( bind ( socket_descriptor,  ( struct sockaddr * ) &sin, sizeof ( sin ) ) < 0 )
	{
		perror ( "bind" );
		exit ( EXIT_FAILURE );
	} /* 在同一个主机上进行广播设置套接口， 作用是方便单个开发系统上测试多播IP广播 */

	loop = 1;

	if ( setsockopt ( socket_descriptor,  IPPROTO_IP, IP_MULTICAST_LOOP,    &loop, sizeof ( loop ) ) < 0 )
	{
		perror ( "setsockopt:IP_MULTICAST_LOOP" );
		exit ( EXIT_FAILURE );
	}   /* 加入一个广播组。进一步告诉Linux内核， 特定的套接口即将接受广播数据*/

	command.imr_multiaddr.s_addr = inet_addr ( "224.0.0.1" );

	command.imr_interface.s_addr = htonl ( INADDR_ANY );

	if ( command.imr_multiaddr.s_addr == -1 )
	{
		perror ( "224.0.0.1 not a legal multicast address" );
		exit ( EXIT_FAILURE );
	}

	if ( setsockopt ( socket_descriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP,    &command, sizeof ( command ) ) < 0 )
	{
		perror ( "setsockopt:IP_ADD_MEMBERSHIP" );
	}

	//while ( iter++ < 20 )/* 接受20个广播后退出 */
	while (  1 )
	{
		if(iter == 10000)iter = 0;else iter++;
		sin_len = sizeof ( sin );

		if ( recvfrom ( socket_descriptor, message, 256, 0,   ( struct sockaddr * ) &sin, &sin_len ) == -1 )
		{
			perror ( "recvfrom" );
		}

		printf ( "Response #%-2d from server: %s\n", iter, message );

		sleep ( 1 );
	}     

//	if ( setsockopt ( socket_descriptor, IPPROTO_IP, IP_DROP_MEMBERSHIP,      &command, sizeof ( command ) ) < 0 )
//	{
//		perror ( "setsockopt:IP_DROP_MEMBERSHIP" );
//	}

	close ( socket_descriptor );

	exit ( EXIT_SUCCESS );
}