一.广播

1.接收

void main()
{SOCKET s = ::socket(AF_INET, SOCK_DGRAM, 0);// 首先要绑定一个本地地址，指明广播端口号SOCKADDR_IN sin;sin.sin_family = AF_INET;sin.sin_addr.S_un.S_addr = INADDR_ANY;    sin.sin_port = ::ntohs(4567);if(::bind(s, (sockaddr*)&sin, sizeof(sin)) == SOCKET_ERROR){printf(" bind() failed \n");return;}// 接收广播printf(" 开始在4567端口接收广播数据... \n\n");SOCKADDR_IN addrRemote;    int nLen = sizeof(addrRemote);char sz[256];while(TRUE){int nRet = ::recvfrom(s, sz, 256, 0, (sockaddr*)&addrRemote, &nLen);if(nRet > 0){sz[nRet] = '\0';printf(sz);}}
}

2.发送

void main()
{SOCKET s = ::socket(AF_INET, SOCK_DGRAM, 0);// 有效SO_BROADCAST选项BOOL bBroadcast = TRUE;::setsockopt(s, SOL_SOCKET, SO_BROADCAST, (char*)&bBroadcast, sizeof(BOOL));
// 设置广播地址，这里的广播端口号（电台）是4567SOCKADDR_IN bcast;bcast.sin_family = AF_INET;bcast.sin_addr.s_addr = INADDR_BROADCAST; // ::inet_addr("255.255.255.255");bcast.sin_port = htons(4567);// 发送广播printf(" 开始向4567端口发送广播数据... \n \n");char sz[] = "This is just a test. \r\n";while(TRUE){::sendto(s, sz, strlen(sz), 0, (sockaddr*)&bcast, sizeof(bcast));::Sleep(5000);}
}

二.IP多播

1.加入多播组并接收数据

void main()
{SOCKET s = ::socket(AF_INET, SOCK_DGRAM, 0);// 允许其它进程使用绑定的地址BOOL bReuse = TRUE;::setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char*)&bReuse, sizeof(BOOL));
// 绑定到4567端口sockaddr_in si;si.sin_family = AF_INET;si.sin_port = ::ntohs(4567);si.sin_addr.S_un.S_addr = INADDR_ANY;::bind(s, (sockaddr*)&si, sizeof(si));// 加入多播组ip_mreq    mcast;mcast.imr_interface.S_un.S_addr = INADDR_ANY;mcast.imr_multiaddr.S_un.S_addr = ::inet_addr("234.5.6.7");  // 多播地址为234.5.6.7::setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*)&mcast, sizeof(mcast));// 接收多播组数据printf(" 开始接收多播组234.5.6.7上的数据... \n");char buf[1280];int nAddrLen = sizeof(si);while(TRUE){int nRet = ::recvfrom(s, buf, strlen(buf), 0, (sockaddr*)&si, &nAddrLen);if(nRet != SOCKET_ERROR){buf[nRet] = '\0';printf(buf);}else{int n = ::WSAGetLastError();break;}}
}

2.发送广播

同上

设置SO_REUSEADDR,则允许多个进程绑定到这个端号,这样加入到同个端口的组都可以接收到数据

三.源地址的IP多播

即可指定接收组内特定IP地址的消息

c#参考：http://www.cnblogs.com/xuhx/archive/2004/06/23/18150.html
http://www.cnblogs.com/xuhx/archive/2004/06/27/18960.html

Windows网络与通信程序设计 第5章