Introduction
When you connect to the server with the address 'www.codeproject.com', your browser needs its numeric representation 69.10.233.10 which it obtains by means of DNS queries. The same process is going on when your mail program needs to send email to a specific domain like webmaster@codeproject.com. Here, it needs to know the mail server for the codeproject domain which is obtained by means of a DNS query. There are other types of queries you may get with DNS on particular domain name. In this article, I provide a nice GUI MFC application with Document/View architecture for performing all types of DNS queries.
Background
The good way to start with DNS is to have a look at the Domain Name System topic on MSDN or SDK help under Networking/Network Protocols part. It describes the basics and provides you with the necessary RFCs to read, e.g. RFC 1034 (Domain Names-Concepts and Facilities-Implementation and Specification-Application and Support), RFC 1035 (Domain Names) and so on.
Using the Code
Make sure first that you are connected to the internet. Press CTRL+Q or go to File menu and click DnsQuery. You will get this dialog box.
Enter the name of the server you want to query, like codeproject.com, choose the type of your query, options and optionally you may use your own default DNS servers or ask for a specific DNS server by typing it in the bottom edit box.
This example provides two queries performed of type A and NS to get numeric address for codeproject.com and its name servers.
In the DNS Query box in the previous image, the DNS server ns.dundas.com is specified to ask it for query type ANY to get all the information about the codeproject.com server.
You can find descriptions for other types of queries in the corresponding RFCs or in the windns.h file:
#define DNS_TYPE_ZERO 0x0000
#define DNS_TYPE_A 0x0001 // 1
#define DNS_TYPE_NS 0x0002 // 2
#define DNS_TYPE_MD 0x0003 // 3
#define DNS_TYPE_MF 0x0004 // 4
#define DNS_TYPE_CNAME 0x0005 // 5
#define DNS_TYPE_SOA 0x0006 // 6
#define DNS_TYPE_MB 0x0007 // 7
#define DNS_TYPE_MG 0x0008 // 8
#define DNS_TYPE_MR 0x0009 // 9
#define DNS_TYPE_NULL 0x000a // 10
#define DNS_TYPE_WKS 0x000b // 11
#define DNS_TYPE_PTR 0x000c // 12
#define DNS_TYPE_HINFO 0x000d // 13
#define DNS_TYPE_MINFO 0x000e // 14
#define DNS_TYPE_MX 0x000f // 15
#define DNS_TYPE_TEXT 0x0010 // 16
#define DNS_TYPE_RP 0x0011 // 17
#define DNS_TYPE_AFSDB 0x0012 // 18
#define DNS_TYPE_X25 0x0013 // 19
#define DNS_TYPE_ISDN 0x0014 // 20
#define DNS_TYPE_RT 0x0015 // 21
#define DNS_TYPE_NSAP 0x0016 // 22
#define DNS_TYPE_NSAPPTR 0x0017 // 23
#define DNS_TYPE_SIG 0x0018 // 24
#define DNS_TYPE_KEY 0x0019 // 25
#define DNS_TYPE_PX 0x001a // 26
#define DNS_TYPE_GPOS 0x001b // 27
#define DNS_TYPE_AAAA 0x001c // 28
#define DNS_TYPE_LOC 0x001d // 29
#define DNS_TYPE_NXT 0x001e // 30
#define DNS_TYPE_EID 0x001f // 31
#define DNS_TYPE_NIMLOC 0x0020 // 32
#define DNS_TYPE_SRV 0x0021 // 33
#define DNS_TYPE_ATMA 0x0022 // 34
#define DNS_TYPE_NAPTR 0x0023 // 35
#define DNS_TYPE_KX 0x0024 // 36
#define DNS_TYPE_CERT 0x0025 // 37
#define DNS_TYPE_A6 0x0026 // 38
#define DNS_TYPE_DNAME 0x0027 // 39
#define DNS_TYPE_SINK 0x0028 // 40
#define DNS_TYPE_OPT 0x0029 // 41
#define DNS_TYPE_UINFO 0x0064 // 100
#define DNS_TYPE_UID 0x0065 // 101
#define DNS_TYPE_GID 0x0066 // 102
#define DNS_TYPE_UNSPEC 0x0067 // 103
#define DNS_TYPE_ADDRS 0x00f8 // 248
#define DNS_TYPE_TKEY 0x00f9 // 249
#define DNS_TYPE_TSIG 0x00fa // 250
#define DNS_TYPE_IXFR 0x00fb // 251
#define DNS_TYPE_AXFR 0x00fc // 252
#define DNS_TYPE_MAILB 0x00fd // 253
#define DNS_TYPE_MAILA 0x00fe // 254
#define DNS_TYPE_ALL 0x00ff // 255
#define DNS_TYPE_ANY 0x00ff // 255
#define DNS_TYPE_WINS 0xff01 // 64K - 255
#define DNS_TYPE_WINSR 0xff02 // 64K - 254
#define DNS_TYPE_NBSTAT (DNS_TYPE_WINSR)
You can also find the description of the query I perform with the DnsQuery() function in MSDN help. I call it in the CDnsView class:
void CDnsView::OnFileDnsquery()
{
PDNS_RECORD pdns;
DNS_FREE_TYPE freetype = DnsFreeRecordList;
in_addr inaddr;
char digit[10];
CDnsDialog dns(¶ms);
if (dns.DoModal() == IDOK) {
message.Format("Q? %s %s %s \r\n", dns.m_name,
Type[params.type].title, params.servers);
pEdit->SetSel(pEdit->GetWindowTextLength(),
pEdit->GetWindowTextLength());
pEdit->ReplaceSel(message);
if (res = DnsQuery(dns.m_name, dns.m_type, dns.m_options,
dns.m_ip4array, &pdns, 0)) {
LPVOID lpMsgBuf;
if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
0, res, MAKELANGID(LANG_NEUTRAL,
SUBLANG_DEFAULT), (LPTSTR)&lpMsgBuf, 0, 0)) {
message.Format("-ERR: %s \r\n",
(LPCTSTR)lpMsgBuf);
pEdit->SetSel(pEdit->GetWindowTextLength(),
pEdit->GetWindowTextLength());
pEdit->ReplaceSel(message);
LocalFree(lpMsgBuf);
} else {
pEdit->SetSel(pEdit->GetWindowTextLength(),
pEdit->GetWindowTextLength());
pEdit->ReplaceSel
("-ERR FormatMessage failed.?\r\n");
}
return;
}
do {
switch (pdns->wType) {
case DNS_TYPE_A:
inaddr.S_un.S_addr = pdns->Data.A.IpAddress;
message.Format(" A %s [%s]", pdns->pName,
inet_ntoa(inaddr));
break;
case DNS_TYPE_NS:
message.Format(" NS %s %s", pdns->pName,
pdns->Data.NS.pNameHost);
break;
case DNS_TYPE_MD:
message.Format(" MD %s %s", pdns->pName,
pdns->Data.MD.pNameHost);
break;
case DNS_TYPE_MF:
message.Format(" MF %s %s", pdns->pName,
pdns->Data.MF.pNameHost);
break;
case DNS_TYPE_CNAME:
message.Format(" CNAME %s %s", pdns->pName,
pdns->Data.CNAME.pNameHost);
break;
case DNS_TYPE_SOA:
message.Format(" SOA %s nameserv: %s\r\n",
pdns->pName, pdns->Data.SOA.pNamePrimaryServer);
temp.Format(" admin: %s\r\n",
pdns->Data.SOA.pNameAdministrator);
message += temp;
temp.Format(" serial: %u\r\n",
pdns->Data.SOA.dwSerialNo);
message += temp;
temp.Format(" refresh: %u\r\n",
pdns->Data.SOA.dwRefresh);
message += temp;
temp.Format(" ttl: %u\r\n",
pdns->Data.SOA.dwDefaultTtl);
message += temp;
temp.Format(" expire: %u\r\n",
pdns->Data.SOA.dwExpire);
message += temp;
temp.Format(" retry: %u",
pdns->Data.SOA.dwRetry);
message += temp;
break;
case DNS_TYPE_MB:
message.Format(" MB %s %s", pdns->pName,
pdns->Data.MB.pNameHost);
break;
case DNS_TYPE_MG:
message.Format(" MG %s %s", pdns->pName,
pdns->Data.MG.pNameHost);
break;
case DNS_TYPE_MR:
message.Format(" MR %s %s", pdns->pName,
pdns->Data.MR.pNameHost);
break;
pdns->Data.Null.MR.pNameHost);
case DNS_TYPE_WKS:
inaddr.S_un.S_addr = pdns->Data.WKS.IpAddress;
message.Format(" WKS %s [%s] proto:
%d mask: %d", pdns->pName,
inet_ntoa(inaddr),
pdns->Data.WKS.chProtocol,
pdns->Data.WKS.BitMask);
break;
case DNS_TYPE_PTR:
message.Format(" PTR %s %s", pdns->pName,
pdns->Data.PTR.pNameHost);
break;
case DNS_TYPE_HINFO:
message.Format(" HINFO %s", pdns->pName);
for (u_int i = 0; i <
pdns->Data.HINFO.dwStringCount; i++) {
message += "\r\n ";
message += pdns->
Data.HINFO.pStringArray[i];
}
break;
case DNS_TYPE_MINFO:
message.Format(" MINFO %s err: %s name: %s",
pdns->pName, pdns->
Data.MINFO.pNameErrorsMailbox,
pdns->Data.MINFO.pNameMailbox);
break;
case DNS_TYPE_MX:
message.Format(" MX %s %s pref: %d",
pdns->pName, pdns->Data.MX.pNameExchange,
pdns->Data.MX.wPreference);
break;
case DNS_TYPE_TEXT:
message.Format(" TEXT %s", pdns->pName);
for (u_int i = 0; i < pdns->
Data.TXT.dwStringCount; i++) {
message += "\r\n ";
message += pdns->
Data.TXT.pStringArray[i];
}
break;
case DNS_TYPE_RP:
message.Format(" RP %s err: %s name: %s",
pdns->pName,
pdns->Data.RP.pNameErrorsMailbox,
pdns->Data.RP.pNameMailbox);
break;
case DNS_TYPE_AFSDB:
message.Format(" AFSDB %s %s pref: %d",
pdns->pName, pdns->Data.AFSDB.pNameExchange,
pdns->Data.AFSDB.wPreference);
break;
case DNS_TYPE_X25:
message.Format(" X25 %s", pdns->pName);
for (u_int i = 0; i <
pdns->Data.X25.dwStringCount; i++) {
message += "\r\n ";
message += pdns->Data.X25.pStringArray[i];
}
break;
case DNS_TYPE_ISDN:
message.Format(" ISDN %s", pdns->pName);
for (u_int i = 0; i <
pdns->Data.ISDN.dwStringCount; i++) {
message += "\r\n ";
message += pdns->Data.ISDN.pStringArray[i];
}
break;
case DNS_TYPE_RT:
message.Format(" RT %s %s pref: %d",
pdns->pName, pdns->Data.RT.pNameExchange,
pdns->Data.RT.wPreference);
break;
case DNS_TYPE_AAAA:
message.Format(" AAAA %s %s pref: %d
[", pdns->pName);
for (int i = 0; i < 16; i++) {
sprintf(digit, "%d",
pdns->Data.AAAA.Ip6Address.IP6Byte[i]);
message += digit;
if (i != 15)
message += ".";
}
message += "]";
break;
case DNS_TYPE_SRV:
message.Format(" SRV %s %s port:%d prior:%d
weight:%d", pdns->pName,
pdns->Data.SRV.pNameTarget,
pdns->Data.SRV.wPort,
pdns->Data.SRV.wPriority,
pdns->Data.SRV.wWeight);
break;
case DNS_TYPE_WINSR:
message.Format(" NBSTAT %s %s",
pdns->pName, pdns->
Data.WINSR.pNameResultDomain);
break;
default:
message.Format(" unknown: %s type %d",
pdns->pName, pdns->wType);
break;
}
if (pdns->Flags.S.Section == DNSREC_AUTHORITY)
message += " (authority)";
if (pdns->Flags.S.Section == DNSREC_ADDITIONAL)
message += " (additional)";
pEdit->SetSel(pEdit->GetWindowTextLength(),
pEdit->GetWindowTextLength());
pEdit->ReplaceSel(message + "\r\n");
pdns = pdns->pNext;
} while (pdns);
pEdit->SetSel(pEdit->GetWindowTextLength(),
pEdit->GetWindowTextLength());
pEdit->ReplaceSel("\r\n");
DnsRecordListFree(pdns, freetype);
}
}
