public void ExecuteTest()
{
Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
byte[] buffer = PrepareDnsQuery();
socket.SendTo(buffer, dnsServerEndPoint);
// Receive the response from the server
byte[] dnsData = new byte[1000];
EndPoint endPoint = (EndPoint)dnsServerEndPoint;
socket.ReceiveFrom(dnsData, ref endPoint);
int index = 0, count = 0;
DnsDiagramHead diagramHead = ParseResponseDiagramHead(dnsData, index, ref count);
index += count;
#region ErrorHandling
if (diagramHead.resRecNum == 0)
{
Console.WriteLine("Could not resolve the host name.");
return;
}
// rcode nonzero means error is found
if ((diagramHead.flag & 0x08) != 0)
{
Console.WriteLine("Dns Error! rcode =%d", (diagramHead.flag & 0x08));
return;
}
#endregion
// Make sure queryNum=1
Debug.Assert(diagramHead.queryNum == 1);
DnsQueryBody queryBody = ParseDnsQueryBody(dnsData, index, ref count);
index += count;
Console.WriteLine("Dns Query Name: " + queryBody.GetQueryNameString());
int resRecordCount = diagramHead.resRecNum;
DnsResourceRecord[] resourceRecords = new DnsResourceRecord[resRecordCount];
for (int i = 0; i < resRecordCount; i++)
{
resourceRecords[i] = ParseDnsResourceRecord(dnsData, index, ref count);
index += count;
}
foreach (DnsResourceRecord record in resourceRecords)
{
Console.WriteLine("Result is " + record.GetResourceContentString());
}
Console.WriteLine("\nPress any key to exit.");
Console.ReadKey();
}
byte[] PrepareDnsQuery()
{
// prepare the head
DnsDiagramHead diagramHead = new DnsDiagramHead();
diagramHead.id = DnsDiagramID;
diagramHead.flag = 0;
diagramHead.flag |= DnsHeadFlag.QRquery | DnsHeadFlag.RD | DnsHeadFlag.TC;
diagramHead.queryNum = 1;
// prepare the body
DnsQueryBody queryBody;
queryBody.queryName = new byte[targetHostName.Length + 1];
for (int i = 0, j = -1; i < targetHostName.Length; i++)
{
if (targetHostName[i] == '.')
{
// j contains the the previous index value of '.' in queryName
queryBody.queryName[j + 1] = (byte)(i - j - 1);
j = i;
}
else
{
queryBody.queryName[i + 1] = (byte)targetHostName[i];
}
}
queryBody.queryName[targetHostName.Length] = 0;
queryBody.queryType = 1; // 'A' address
queryBody.queryClass = 1; // IP address
int bufferSize = diagramHead.DiagramSize + queryBody.DiagramSize;
byte[] buffer = new byte[bufferSize];
int index = 0;
diagramHead.ToByteArray().CopyTo(buffer, index);
index += diagramHead.DiagramSize;
queryBody.ToByteArray().CopyTo(buffer, index);
index += queryBody.DiagramSize;
return(buffer);
}
DnsDiagramHead ParseResponseDiagramHead(byte[] buffer, int beginIndex, ref int parseCount)
{
DnsDiagramHead diagramHead = new DnsDiagramHead();
int index = beginIndex;
diagramHead.id = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
diagramHead.flag = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
diagramHead.queryNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
diagramHead.resRecNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
diagramHead.autResRecNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
diagramHead.extResRecNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, index));
index += sizeof(Int16);
parseCount = index - beginIndex;
return(diagramHead);
}
