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POGot local host name, working on windows, but not in Linux
 

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  1. POGot local host name, working on windows, but not in Linux
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    <p>I wrote a program to get local host name. if it is not obvious, I mean to get the host name of the local machine similar to <code>gethostname</code> method, not to get the string <code>localhost</code></p> <p>I'm using <code>getaddrinfo</code> with <code>NULL</code> for host name and then call to <code>getnameinfo</code> with the first address.</p> <p>It works perfectly on windows machines, and giving me the canonical host name, but in Linux it failed to give me the local host name and gives me <code>::</code> for IPv6 or <code>0.0.0.0</code> for IPv4.</p> <p>Note that I'm using <code>AI_PASSIVE</code> flag in <code>getaddrinfo</code>, means it gives me no more than two addresses.</p> <p>In the <code>getnameinfo</code> if I use the <code>NI_NAMEREQD</code> it fail.</p> <p>I'm doing so because I have a server, sometimes I want to listen to all interfaces and sometimes to a specific interface, I'm already have the <code>addrinfo</code> and I just want to get the hostname from it if possible.</p> <p>How can I make it work on Linux? did I missed anything?</p> <p>Thanks for any help.</p> <p>Here is my code: (cross platform, windows and Linux, just copy &amp; past) You can compile and run on both and see the difference.</p> <pre><code>#include &lt;iostream&gt; #ifdef WIN32 #ifdef UNICODE #undef UNICODE /* don't want Unicode, to keep code compatibility */ #endif #include &lt;WS2tcpip.h&gt; #pragma comment(lib, "ws2_32.lib") class CWSAInitializer{ public: CWSAInitializer(){ WSADATA data; WSAStartup(MAKEWORD(2,2),&amp;data); } ~CWSAInitializer(){ WSACleanup(); } }autoInit; #else #include &lt;sys/types.h&gt; #include &lt;sys/socket.h&gt; #include &lt;netdb.h&gt; #endif const char* get_hostname(struct addrinfo* info, char buff[], int buff_len) { int addrlen = (int)info-&gt;ai_addrlen; int res = getnameinfo(info-&gt;ai_addr, addrlen, buff, buff_len, NULL, 0, 0); if(res){ return NULL; } return buff; } int main () { char temp[100]; addrinfo *ai,hints; memset(&amp;hints,0,sizeof(hints)); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_NUMERICSERV; hints.ai_flags |= AI_PASSIVE; int res = getaddrinfo(NULL, "0", &amp;hints, &amp;ai); if(res){ std::cerr&lt;&lt;gai_strerror(res)&lt;&lt;std::endl; return -1; } std::cout&lt;&lt; get_hostname(ai,temp,100)&lt;&lt;std::endl; freeaddrinfo(ai); return 0; } </code></pre> <p><strong>EDIT</strong></p> <ol> <li><p>The server should accept client from other machines as well, so it can't report listening on <code>::</code> or <code>0.0.0.0</code>. </p></li> <li><p>I know I can patch it like this: </p></li> </ol> <p><code>if(std::string("::") == hostname || std::string("0.0.0.0") == hostname) gethostname(hostname,100)</code></p> <ol start="3"> <li>I don't want to get <code>localhost</code> as result, unless the address is <code>127.0.0.1</code> or <code>::1</code>.</li> </ol>
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      1. POGot local host name, working on windows, but not in Linux
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    1. COIf you ONLY want the local host name, why don't you use INADDR_LOOPBACK?
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    2. COI don't want the localhost interface. the server is listenning outside, I want to know which **hostname** I'm currently listenning. If client would try to connect to :: or to 0.0.0.0 it won't connect.
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