如何获得套接字的稳定主机名？

Question

With an open socket accepted by a listen socket I want to get the hostname of the remote end. Using getnameinfo() for hosts that have multiple hostnames I don't always get the same hostname. Is it possible to get all of them or at least get the same one each time?

I've read in some docs something about a canonical hostname but can't find more information beyond a suggesting that this is what I need.

Here's how I call getnameinfo()

char szHostname[ NI_MAXHOST ];
const sockaddr* pSock;
int nSockLen;

// stuff to get a pSock

int ret = getnameinfo( pSock, nSockLen, szHostname, NI_MAXHOST, 0, 0, NI_NAMEREQD );
if ( ret != 0 )
    ret = getnameinfo( pSock, nSockLen, szHostname, NI_MAXHOST, 0, 0, NI_NUMERICHOST );

printf( szHostname );

If a peer X has multiple hostnames AAA & BBB szHostname could have either.

Answer 1

Use gethostbyaddr() , it will gives you all DNS entries for your internet address (IPv4 only). The first one should be the canonical one. If you need IPv6, then (if think that) you should use getaddrinfo() and set the AI_CANONNAME in the hints (see manual).