gethostbyaddr 在 Windows 上可以，但在 Linux 上返回 NULL [英] gethostbyaddr is OK on Windows but returns NULL on Linux

问题描述

这段代码在 Windows 上运行正常，但在 Linux 上 gethostbyaddr 返回 NULL.

This piece of code works OK on windows, but gethostbyaddr returns NULL on Linux.

我尝试了很多更改，但都没有成功.

I have tried so many changes, but without any success.

我的/etc/host.conf 有以下行

My /etc/host.conf has the following line

订购主机，绑定

我运行完整代码并传递地址 11.234.456.74，在 Windows 上 gethostbyaddr 解析地址并且工作正常.但是在 Linux 上它不解析 ip 地址并返回 NULL.

I run the full code and pass address 11.234.456.74, On windows gethostbyaddr resolves the address and works fine. However on Linux it does not resolve the ip address and returns NULL.

请帮忙.

#ifdef WIN32
if (init){
    WSADATA wsaData;
    // Request Winsock version 2.2
    if (WSAStartup (MAKEWORD(1, 1), &wsaData) != 0) {
        WSACleanup();
        exit (EXIT_FAILURE);
    }
    init = 0;
}   
#endif

// Open required socket
p_socket[IP_SOCKET_SOCKET] = socket(AF_INET, server_socket_type, 0);
if ( p_socket[IP_SOCKET_SOCKET] < 0 ) {
#ifdef WIN32
    WSACleanup();
#endif
    exit (EXIT_FAILURE);
}
destAdrLen = mxGetM(prhs[0]) * mxGetN(prhs[0]) + 1;
destAdr  = (char *) mxMalloc(destAdrLen);
if (destAdr == NULL) {
    mexErrMsgTxt("mxMalloc(destAdrLen) failed");
}
mxGetString(prhs[0], destAdr, destAdrLen);

destPort = (int) mxGetScalar(prhs[1]);

if (isalpha(destAdr[0])) { 
    // socket address is a name
    hp = gethostbyname(destAdr);
}
else {      
    // socket address is a number
    addr = inet_addr(destAdr);
    hp = gethostbyaddr((char *)&addr, 4, AF_INET);
}

推荐答案

该主机似乎没有注册反向 dns 记录.

That host doesn't appear to have a reverse dns record registered.

$ dig -x 11.234.217.74

; <<>> DiG 9.9.1-P2 <<>> -x 11.234.217.74
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 30231
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;74.217.234.11.in-addr.arpa.    IN  PTR

;; AUTHORITY SECTION:
in-addr.arpa.       3599    IN  SOA b.in-addr-servers.arpa. nstld.iana.org. 2011026180 1800 900 604800 3600

;; Query time: 1217 msec

所以对 gethostbyaddr 的调用将失败.herror 函数甚至会打印 Unknown host 的消息.如果您想在这些情况下保留数字 IP，则必须自己编写该代码路径.如果 Windows 做了其他任何事情，看看它从哪里获取信息会很有趣.

So the call to gethostbyaddr will fail. The herror function will even print a message of Unknown host. If you want to keep the numeric IP in those cases, you'll have to write that code path yourself. If Windows does anything else, it would be interesting to see where it got its information from.

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