c语言 域名解析

c语言中怎么做域名解析

九三
266
2021-02-09 10:30:46
栏目: 云计算

c语言中怎么做域名解析

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;

}

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