static void Main(string[] args)
{
// Start P2P thread
Thread p2pListener = new Thread(new ThreadStart(P2P.Run));
p2pListener.Start();
// Open UDP socket
UdpClient listener = new UdpClient(listenPort);
IPEndPoint groupEP;
// Receive a packet
try
{
byte[] recv_buf;
while (true)
{
// Set listen address
groupEP = new IPEndPoint(IPAddress.Any, listenPort);
// Receive data, client will be placed in groupEP
recv_buf = listener.Receive(ref groupEP);
// Parse DNS data
MemoryStream ms = new MemoryStream(recv_buf);
BinaryReader br = new BinaryReader(ms);
DNS_header header = new DNS_header();
header.Read(br);
if (header.QDcount != 1)
{
Console.WriteLine("Cannot parse DNS request where QDcount != 1");
continue;
}
DNS_question question = new DNS_question();
question.Read(br);
// Get the answer to the query
byte[] ans_ip = new byte[4];
DNScache.resolve(question.name, ref ans_ip);
// Send a response
MemoryStream ms_out = new MemoryStream();
BinaryWriter bw = new BinaryWriter(ms_out);
// Modify DNS header
header.qr = true;
header.rcode = 0;
header.ANcount = 1;
// Write DNS header
header.Write(bw);
// Write question
question.Write(bw);
// Generate answer
DNS_answer answer = new DNS_answer();
answer.name = question.name;
answer.atype = 1;
answer.aclass = 1;
answer.ttl = 60;
answer.rdlen = 4;
answer.rdata = ans_ip;
// Write answer
answer.Write(bw);
// Send the packet
byte[] buf_out = ms_out.ToArray();
listener.Send(buf_out, buf_out.Length, groupEP);
}
} catch (Exception e)
{
Console.WriteLine(e.ToString());
Console.ReadLine();
}
p2pListener.Interrupt();
}
public static void Run()
{
UdpClient udpClient = new UdpClient();
udpClient.EnableBroadcast = true;
IPEndPoint recv_groupep = new IPEndPoint(IPAddress.Any, _P2P_PORT);
udpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
udpClient.ExclusiveAddressUse = false;
udpClient.Client.Bind(recv_groupep);
while (true)
{
IPEndPoint recv_ipep = null;
try
{
byte[] packet = udpClient.Receive(ref recv_ipep);
MemoryStream ms = new MemoryStream(packet);
BinaryReader br = new BinaryReader(ms);
UInt32 id = br.ReadUInt32();
byte isRequest = br.ReadByte();
if (isRequest == 1)
{
string name = DNS.ReadName(br);
DNScache.clean();
lock (DNScache._lock_cache)
{
if (DNScache._cache.ContainsKey(name))
{
MemoryStream ms_res = new MemoryStream();
BinaryWriter bw = new BinaryWriter(ms_res);
bw.Write(id);
bw.Write((byte)0);
DNScache.cache_entry ce = DNScache._cache[name];
if (ce.success)
{
bw.Write((byte)1);
UInt32 ttl = (UInt32)((ce.expiry - DateTime.Now).TotalSeconds);
bw.Write((UInt32)IPAddress.HostToNetworkOrder((int)ttl));
bw.Write(ce.address, 0, 4);
}
else
{
bw.Write((byte)0);
UInt32 ttl = (UInt32)((ce.expiry - DateTime.Now).TotalSeconds);
bw.Write((UInt32)IPAddress.HostToNetworkOrder((int)ttl));
bw.Write((byte)0);
bw.Write((byte)0);
bw.Write((byte)0);
bw.Write((byte)0);
}
byte[] packet_res = ms_res.ToArray();
udpClient.Send(packet_res, packet_res.Length, recv_ipep);
}
}
}
} catch (ThreadInterruptedException ex) {
return;
}
}
}