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POSocket transmit data but can't receive response
 

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    <p>I am trying to implement UpNP in C++, I found a few sources on google but none worked. I found this one working (<a href="http://www.codeproject.com/KB/IP/upnplib.aspx" rel="nofollow noreferrer">http://www.codeproject.com/KB/IP/upnplib.aspx</a>) but it's for .NET, so I decided to sniff the network to see what the code was doing and then do the same with sockets.</p> <p>Here are the results (full size: <a href="https://i.stack.imgur.com/eLoHK.jpg" rel="nofollow noreferrer">http://i.stack.imgur.com/eLoHK.jpg</a>): <img src="https://i.stack.imgur.com/eLoHK.jpg" alt="enter image description here"></p> <p>That shows me that the packet doesn't look bad, everything seems to be the same, everything but the <strong>source address</strong> of my code, which I don't know how to control (both my code and finder.net.exe are being tested on the same computer connected to the same network).</p> <p>Here's my code:</p> <pre><code>#define upnp_broadcast_ip "239.255.255.250" #define upnp_broadcast_port 1900 #define upnp_search_request "M-SEARCH * HTTP/1.1\r\n" \ "Host:239.255.255.250:1900\r\n" \ "ST:upnp:rootdevice\r\n" \ "Man:\"ssdp:discover\"\r\n" \ "MX:3\r\n" \ "\r\n" WSAStartup(MAKEWORD(2, 2), &amp;WsaData); BOOL discover( ) { SOCKET ConnectSocket; struct sockaddr_in Addr; char Buffer[1450]; int t = 0, iResult = 0, TrueLen = sizeof(bool); bool True = true; ulong One = 1; // Open datagram socket ConnectSocket = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP ); // Clear out struct memset( &amp;Addr, 0, sizeof(Addr) ); // Specify the address family, IP address, and port Addr.sin_family = AF_INET; Addr.sin_port = htons( upnp_broadcast_port ); Addr.sin_addr.s_addr = inet_addr( upnp_broadcast_ip ); iResult = setsockopt( ConnectSocket, SOL_SOCKET, SO_BROADCAST, (char*)&amp;True, TrueLen ); // Not sure what is this for // Transmit data int sent = sendto( ConnectSocket, upnp_search_request, strlen(upnp_search_request), 0, (struct sockaddr*)&amp;Addr, sizeof(Addr) ); // Try to receive data 10 times for( t = 0; t &lt; 10; t++ ) { ioctlsocket( ConnectSocket, FIONBIO, &amp;One ); // Clear out buffer memset( &amp;Buffer, 0, sizeof(Buffer) ); int length = sizeof(Addr); // Receive data iResult = recvfrom( ConnectSocket, Buffer, (sizeof(Buffer) - 1), 0, (struct sockaddr*)&amp;Addr, &amp;length ); if( iResult == SOCKET_ERROR) { Sleep( 1000 ); continue; } else { // Do stuff with received data } } closesocket( ConnectSocket ); return FALSE; } </code></pre> <p>I removed all the WSAGetLastError() error checking to make the code easier to read, everything goes fine until recvfrom, that always returns -1 and strerror(WSAGetLastError()) prints "Unknown error".</p> <p>I hope someone could guide me in the right direction, I've been the last two days trying to make this work.</p>
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    1. COIMHO, you shouldn't change the question so drastically: you can create a new question for the way to get the IP address you're looking for, but right now, the title is misleading and you got an answer to the original question...
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