VC编程用UPD协议实现广播通信

a.sin_family=AF_INET;
a.sin_addr.s_addr=0;
a.sin_port=htons(5050);

from.sin_family=AF_INET;
from.sin_addr.s_addr=INADDR_BROADCAST;
from.sin_port=htons(5050);
int fromlength=sizeof(SOCKADDR);
//用UDP初始化套接字
s=socket(AF_INET,SOCK_DGRAM,0);
//设置该套接字为广播类型，
setsockopt(s,SOL_SOCKET,SO_BROADCAST,(char FAR *)&optval,sizeof(optval));
//把该套接字绑定在一个具体的地址上
bind(s,(sockaddr *)&a,sizeof(sockaddr_in));
char buf[256];
while(1)
{ //从广播地址接收消息，注意用来绑定的地址和接收消息的地址是不一样的
recvfrom(s,buf,256,0,(struct sockaddr FAR *)&from,(int FAR *)&fromlength);
Sleep(2000);
printf("%s\n",buf);
ZeroMemory(buf,256);
}
.....