使用c语言实现域名解析的方法
c语言代码如下：
#include
#include
#include
typedef enum {false = 0, true = !false}bool;
typedef struct _DNSHEAD{ //dns 头部
USHORT ID;
USHORT tag; // dns 标志(参数)
USHORT numQ; // 问题数
USHORT numA; // 答案数
USHORT numA1; // 权威答案数
USHORT numA2; // 附加答案数
}DnsHead;
typedef struct _DNSQUERY //dns 查询结构
{
// char name[64];
// //查询的域名,这是一个大小在0到63之间的字符串；
USHORT type;
//查询类型，大约有20个不同的类型
USHORT classes;
//查询类,通常是A类既查询IP地址。
}DnsQuery;
#pragma comment(lib,"ws2_32.lib")
// 初始化操作
bool initWSA();
//显示错误
void displayErrWSA(char *str);
//创建套接字
SOCKET CreateSocket(int type);
//UDP sendto
int MySendto(SOCKET sockTo, const char FAR * buf,int len,char *addr,USHORT port);
//TCP 连接
bool MyConnect(SOCKET s, char *addr,USHORT );
// UDP recvfrom
int MyRecvFrom(SOCKET s, char FAR * buf,int len,char *addr,USHORT port);
//设置DNS 头部
bool SetDNSHead(char *name,char *buf);
int main(int arg,char *are[])
{
int Result=0;
char buf[1024]={0};
char addr[16] = "192.168.1.1";// dns 服务器地址
char *name = 0; //要查询的域名
SOCKET sockTo;
int len;
DnsHead *DnsH;
char *getIP;
//int i;
if ( !initWSA() )//初始化
{
displayErrWSA("initWSA err!");
return 1;
}
//创建套接字
if ( (sockTo = CreateSocket(SOCK_DGRAM)) == 0)
{
displayErrWSA("CreatSocket err!");
return 1;
}
while (1)
{
if (arg < 2)
{
char temp[1024]={0};
printf("\n请输入要查询的域名:");
scanf("%s",temp);
if (temp[0] == 'q' ||temp[0] == 'Q')
{
break;
}
name = temp;
}
else
{
arg = 1;
name = are[1];
}
//设置dns 头部
SetDNSHead(name,buf);
//发送出去的请求数据长度
len = sizeof(DnsHead)+sizeof(DnsQuery)+strlen(name)+2;
// for (int i =0;i<50;i+=2)
// {
// printf("x",(UCHAR)buf[i]);
// printf("x ",(UCHAR)buf[i+1]);
// }
//发送DNS 请求
if ( ( Result =MySendto(sockTo,buf,len,addr,53) ) <= 0)
{
displayErrWSA("sendto err!");
continue;
}
//接收应答
if ( (Result =MyRecvFrom(sockTo,buf,1024,addr,53) ) <= 0)
{
displayErrWSA("recvfrom err!");
continue;
}
//简单的取得返回的 IP 地址( 收到的最后4字节 )
DnsH = (DnsHead *)buf;
if (DnsH->numA == 0)
{
printf("无法解析 %s 的IP 地址。\n",name);
continue;
}
getIP =(char *)buf +Result - 4;
printf("%s 的IP地址为: ",name);
for (Result= 0 ;Result<4 ;Result++)
{
printf("%u.",(UCHAR )getIP[Result]);
}
printf("\n");
}
return 0;
}
// 初始化操作
bool initWSA()
{
WORD wVersionRequested;
WSADATA wsaData;
int Result;
wVersionRequested = MAKEWORD( 2, 2 );
Result = WSAStartup( wVersionRequested, &wsaData );
if(Result != 0 )
{
return false;
}
if( LOBYTE( wsaData.wVersion) != 2 ||
HIBYTE(wsaData.wVersion)!= 2 )
{
WSACleanup();
return false;
}
return true;
}
SOCKET CreateSocket(int type)
{
SOCKET sock=socket(AF_INET,type,0);
if (sock == INVALID_SOCKET )
{
return 0;
}
return sock;
}
int MySendto(SOCKET sockTo, const char FAR * buf,int len,char *addr,USHORT port)
{
//设置发送数据到的 套接字及地址结构
SOCKADDR_IN addrTo;
addrTo.sin_addr.S_un.S_addr=inet_addr(addr);
addrTo.sin_family=AF_INET;
addrTo.sin_port=htons(port);
return sendto( sockTo, buf, len, 0,
(struct sockaddr *)&addrTo, sizeof(struct sockaddr) );
}
bool MyConnect(SOCKET sockTo, char *addr,USHORT port)
{
int Result;
//设置连接到的 套接字及地址结构
SOCKADDR_IN addrTo;
addrTo.sin_addr.S_un.S_addr=(inet_addr(addr));
addrTo.sin_family=AF_INET;
addrTo.sin_port=htons(port);
//连接
Result = connect(sockTo,(struct sockaddr *)&addrTo,sizeof(SOCKADDR_IN));
if(SOCKET_ERROR == Result)
{
return false;
}
return true;
}
int MyRecvFrom(SOCKET s, char FAR * buf,int len,char *addr,USHORT port)
{
//设置发送数据到的 套接字及地址结构
int addrlen;
SOCKADDR_IN addrFrom;
addrFrom.sin_addr.S_un.S_addr=inet_addr(addr);
addrFrom.sin_family=AF_INET;
addrFrom.sin_port=htons(port);
addrlen = sizeof(SOCKADDR_IN);
return recvfrom( s, buf, len, 0, (SOCKADDR *)&addrFrom, &addrlen);
}
int ChName(char *fname,char *tname);//域名转化
bool SetDNSHead(char *name,char *buf)
{
DnsHead *DnsH;
DnsQuery *DnsQ;
int NameLen;
memset(buf,0,sizeof(DnsHead));
//设置头部
DnsH = (DnsHead *)buf;
DnsH->ID = (USHORT)1;
DnsH->tag = htons(0x0100);
DnsH->numQ = htons(1);
DnsH->numA = 0;
DnsQ =(DnsQuery *) ( buf+ sizeof(DnsHead) );
NameLen = ChName(name,(char *)DnsQ);
//设置查询信息
DnsQ = (DnsQuery *)( (char *)DnsQ + NameLen );
DnsQ->classes = htons(1);
DnsQ->type = htons(1);
return true;
}
//显示错误信息
void displayErrWSA(char *str)
{
printf("\n%s,err = %d\n",str,WSAGetLastError());
getchar();
}
//域名转化
int ChName(char *fname,char *tname)
{
int j =0;
int i =strlen(fname)-1;
int k = i+1;
tname[i+2] = 0;
for (; i>=0;i--,k--)
{
if (fname[i] == '.')
{
tname[k] = j;
j=0;
}
else
{
tname[k] = fname[i];
j++;
}
}
tname[k] = j;
return strlen(tname)+1;
}
