UDP获取服务器IP地址？

[a3622041]

WORD wVersionRequested;
	WSADATA wsaData;
	int err;

	wVersionRequested = MAKEWORD( 2, 2 );
	err = WSAStartup( wVersionRequested, &wsaData );
	if ( err != 0 )
	{
		return;
	}

   if ( LOBYTE( wsaData.wVersion ) != 2 ||HIBYTE( wsaData.wVersion ) != 2 )
	{
		 WSACleanup( );
		return; 
	}
    SOCKET sSrv;
    sockaddr_in addrto;
    WSADATA wsdata;
    BOOL bsocket;
   char buff[255] = ""; 
   sSrv=WSASocket(AF_INET,SOCK_DGRAM,0,NULL,0,WSA_FLAG_OVERLAPPED);
    bsocket=TRUE;
    //然后赋值给地址，用来从网络上的广播地址接收消息；
    addrto.sin_family=AF_INET;
    addrto.sin_addr.s_addr=INADDR_BROADCAST;
    addrto.sin_port=htons(8900); // 与服务器端的相同
    //设置该套接字为广播类型
    BOOL bSetBroadcast=TRUE;
    setsockopt(sSrv,SOL_SOCKET,SO_BROADCAST,(char FAR *)&bSetBroadcast,sizeof(bSetBroadcast));
    char    szMsg[]="Get IPAddr";
    int nLen=sizeof(addrto);
    if( SOCKET_ERROR==sendto(sSrv, szMsg, strlen(szMsg), 0, (sockaddr*)&addrto, nLen) )
        MessageBox(NULL,"Send UDP Failed","",MB_OK);   
	while(true)   
    {   
        // 接收数据   
        int nSendSize = recvfrom(sSrv, buff, 255, 0, (SOCKADDR*)&addrto,&nLen);   
        if(SOCKET_ERROR == nSendSize)   
        {   
           int err = WSAGetLastError();   
            printf("\"recvfrom\" error! error code is %d\n", err);   
            return ;   
        }   
        buff[nSendSize] = '\0';   
        printf("received ip: %s\n", buff);   
    }   

[a3622041]

addrto.sin_port=htons(8900); 断电看 这个值为什么为addrto.sin_port=50210

[worldy]

int nSendSize = recvfrom(sSrv, buff, 255, 0, (SOCKADDR*)&addrto,&nLen); 红色包含有返回的发送方的地址和端口信息

[a3622041]

引用 2 楼 worldy 的回复:

int nSendSize = recvfrom(sSrv, buff, 255, 0, (SOCKADDR*)&addrto,&nLen); 红色包含有返回的发送方的地址和端口信息

断点看那个值是空的

[worldy]

recvfrom The Windows Sockets recvfrom function receives a datagram and stores the source address. int recvfrom ( SOCKET s, char FAR* buf, int len, int flags, struct sockaddr FAR* from, int FAR* fromlen ); Parameters s [in] A descriptor identifying a bound socket. buf [out] A buffer for the incoming data. len [in] The length of buf. flags [in] An indicator specifying the way in which the call is made. from [out] An optional pointer to a buffer that will hold the source address upon return. fromlen [in/out] An optional pointer to the size of the from buffer. 检查nSendSize是否为大于0的数，如果是，则from参数应该不会空