public static int socket(int family, int type, int protocol)
{
if (!_isInitialized)
{
Initialize();
}
switch (family)
{
case 2: /* InterNetwork */
{
switch (type)
{
case 1: /* Stream */
{
if (protocol == 6 /* Tcp */)
{
return(_ipv4Layer.CreateSocket(IPv4Layer.ProtocolType.Tcp, Int64.MaxValue));
}
}
break;
case 2: /* Dgram */
{
if (protocol == 17 /* Udp */)
{
return(_ipv4Layer.CreateSocket(IPv4Layer.ProtocolType.Udp, Int64.MaxValue));
}
}
break;
}
}
break;
}
/* if we could not create a socket, return -1. */
return(-1);
}
bool SendDnsQueryAndWaitForResponse(UInt32 dnsServerIPAddress, DnsRecordType recordType, string name, out DnsResponse dnsResponse, Int64 timeoutInMachineTicks)
{
// obtain an exclusive handle to the reserved socket
int socketHandle = _ipv4Layer.CreateSocket(IPv4Layer.ProtocolType.Udp, timeoutInMachineTicks, true);
// instantiate the reserved socket
UdpSocket socket = (UdpSocket)_ipv4Layer.GetSocket(socketHandle);
try
{
// create DNS request header
byte[] dnsRequestBuffer = new byte[DNS_FRAME_BUFFER_LENGTH];
int bufferIndex = 0;
/* Transaction ID */
UInt16 transactionID = _nextTransactionID++;
dnsRequestBuffer[bufferIndex++] = (byte)((transactionID >> 8) & 0xFF);
dnsRequestBuffer[bufferIndex++] = (byte)(transactionID & 0xFF);
/* Flags (including OpCode and RCODE) */
DnsMessageFlagsFlags flags = 0;
/* QR = 0 (query)
* OpCode = 0 (standard query/response)
* RD = 1 (recursion desired) */
flags |= DnsMessageFlagsFlags.RecursionDesired;
dnsRequestBuffer[bufferIndex++] |= (byte)(((UInt16)flags >> 8) & 0xFF);
dnsRequestBuffer[bufferIndex++] |= (byte)((UInt16)flags & 0xFF);
/* Query Count */
UInt16 queryCount = 1;
dnsRequestBuffer[bufferIndex++] = (byte)((queryCount >> 8) & 0xFF);
dnsRequestBuffer[bufferIndex++] = (byte)(queryCount & 0xFF);
/* Answer Count */
// skip bytes 6-7
bufferIndex += 2;
/* Authority Record Count */
// skip bytes 8-9
bufferIndex += 2;
/* Additional Information Count */
// skip bytes 10-11
bufferIndex += 2;
// create dns question (query)
// Query Name
Int32 namePosition = 0;
while (true)
{
Int32 labelLength = name.IndexOf('.', namePosition) - namePosition;
if (labelLength < 0)
{
bufferIndex++;
break;
}
dnsRequestBuffer[bufferIndex++] = (byte)labelLength;
Int32 labelLengthVerify = System.Text.Encoding.UTF8.GetBytes(name, namePosition, labelLength, dnsRequestBuffer, bufferIndex);
// if the label was not decoded as 8-bit characters, throw an exception; international punycode-encoded domains are not supported.
if (labelLengthVerify != labelLength)
{
throw new ArgumentException();
}
namePosition += labelLength + 1;
bufferIndex += labelLength;
}
// Query Type
dnsRequestBuffer[bufferIndex++] = (byte)((((UInt16)recordType) >> 8) & 0xFF);
dnsRequestBuffer[bufferIndex++] = (byte)(((UInt16)recordType) & 0xFF);
// Query Class
UInt16 queryClass = DNS_RECORD_CLASS_INTERNET;
dnsRequestBuffer[bufferIndex++] = (byte)((queryClass >> 8) & 0xFF);
dnsRequestBuffer[bufferIndex++] = (byte)(queryClass & 0xFF);
/* NOTE: this implementation queries the primary DNS address */
// send DNS request
socket.SendTo(dnsRequestBuffer, 0, bufferIndex, 0, timeoutInMachineTicks, dnsServerIPAddress, DNS_SERVER_PORT);
// wait for DNS response
bool success = RetrieveDnsResponse(socket, transactionID, out dnsResponse, timeoutInMachineTicks);
if (success)
{
return(true);
}
}
finally
{
// close the reserved socket
_ipv4Layer.CloseSocket(socketHandle);
}
return(false); /* could not retrieve DNS response */
}