域名解析【网络程序设计

实验要求

给出域名，调用WindowsAPI，解析域名，返回其IPV4地址。

Code

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <windows.h>
#pragma comment(lib, "ws2_32.lib")

int main(int argc, char **argv)
{

    //-----------------------------------------
    // Declare and initialize variables
    WSADATA wsaData;
    int iResult;

    DWORD dwError;
    int i = 0;

    struct hostent *remoteHost;
    char *host_name;
    struct in_addr addr;

    char **pAlias;

    // Validate the parameters
    if (argc != 2) {
        printf("usage: %s hostname
", argv[0]);
        printf("  to return the IP addresses for the host
");
        printf("       %s www.contoso.com
", argv[0]);
        printf(" or
");
        printf("       %s IPv4string
", argv[0]);
        printf("  to return an IPv4 binary address for an IPv4string
");
        printf("       %s 127.0.0.1
", argv[0]);
        return 1;
    }
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d
", iResult);
        return 1;
    }

    host_name = argv[1];

    printf("Calling gethostbyname with %s
", host_name);
    remoteHost = gethostbyname(host_name);
    
    if (remoteHost == NULL) {
        dwError = WSAGetLastError();
        if (dwError != 0) {
            if (dwError == WSAHOST_NOT_FOUND) {
                printf("Host not found
");
                return 1;
            } else if (dwError == WSANO_DATA) {
                printf("No data record found
");
                return 1;
            } else {
                printf("Function failed with error: %ld
", dwError);
                return 1;
            }
        }
    } else {
        printf("Function returned:
");
        printf("	Official name: %s
", remoteHost->h_name);
        for (pAlias = remoteHost->h_aliases; *pAlias != 0; pAlias++) {
            printf("	Alternate name #%d: %s
", ++i, *pAlias);
        }
        printf("	Address type: ");
        switch (remoteHost->h_addrtype) {
        case AF_INET:
            printf("AF_INET
");
            break;
        case AF_NETBIOS:
            printf("AF_NETBIOS
");
            break;
        default:
            printf(" %d
", remoteHost->h_addrtype);
            break;
        }
        printf("	Address length: %d
", remoteHost->h_length);

        i = 0;
        if (remoteHost->h_addrtype == AF_INET)
        {
            while (remoteHost->h_addr_list[i] != 0) {
                addr.s_addr = *(u_long *) remoteHost->h_addr_list[i++];
                printf("	IP Address #%d: %s
", i, inet_ntoa(addr));
            }
        }
        else if (remoteHost->h_addrtype == AF_NETBIOS)
        {   
            printf("NETBIOS address was returned
");
        }   
    }

    return 0;
}

程序说明

编译：gcc -fexec-charset=GBK gethostbyname.c -o gethostbyname -lws2_32
执行

1. 不带参数 gethostbyname
2. 带参数 gethostbyname www.baidu.com

实验截图

参考资料

1.gethostbyname API