private RTLMessage ReceiveAVRMsg(StreamReader sr)
{
RTLMessage msg = new RTLMessage();
// read AVR format input
msg.RawMessage = sr.ReadLine();
if (msg.RawMessage.StartsWith("*"))
{
// standard AVR message
// no timestamp in telegram --> set timestamp after reading
msg.TimeStamp = DateTime.UtcNow;
msg.SignalStrength = 0;
}
else if (msg.RawMessage.StartsWith("@"))
{
// extended AVR message wit MLAT
// convert into standard message format
// extract time string
string time = msg.RawMessage.Substring(1, 12);
// TODO: interprete the MLAT timestamp!
msg.TimeStamp = DateTime.UtcNow;
msg.RawMessage = "*" + msg.RawMessage.Remove(0, 13);
}
return(msg);
}
private RTLMessage ReceiveBinaryMsg(Stream stream)
{
// read Mode-S beast binary input
string RTL = null;
int signal_strength = 0;
long nanosec = 0;
long daysec = 0;
DateTime timestamp = DateTime.UtcNow;
byte[] buffer = new byte[23];
// wait for escape character
DateTime start = DateTime.UtcNow;
DateTime stop = DateTime.Now;
do
{
stream.Read(buffer, 0, 1);
// System.Console.WriteLine(BitConverter.ToString(buffer,0,1));
if (buffer[0] == 0x1A)
{
// read next character
stream.Read(buffer, 1, 1);
switch (buffer[1])
{
case 0x31:
// do not decode
RTL = null;
break;
case 0x32:
// 7 byte short frame
// read timestamp
stream.Read(buffer, 2, 6);
nanosec = ((buffer[4] & 0x3f) << 24) |
(buffer[5] << 16) |
(buffer[6] << 8) |
(buffer[7]);
daysec = (buffer[2] << 10) |
(buffer[3] << 2) |
(buffer[4] >> 6);
timestamp = DateTime.Today.AddSeconds(daysec);
timestamp = timestamp.AddMilliseconds(nanosec / 1000);
// plausibility check
if (Math.Abs((DateTime.Now - timestamp).Seconds) > 10)
{
// time difference > 10sec --> discard timestamp
timestamp = DateTime.UtcNow;
}
// read signal strength
stream.Read(buffer, 8, 1);
// plausibility check
if (Math.Abs((DateTime.Now - timestamp).Seconds) > 10)
{
// time difference > 10sec --> discard timestamp
timestamp = DateTime.UtcNow;
}
signal_strength = buffer[8];
// read frame
stream.Read(buffer, 9, 7);
// convert to AVR string
RTL = BitConverter.ToString((byte[])buffer, 9, 7).Replace("-", String.Empty);
RTL = "*" + RTL + ";";
break;
case 0x33:
// 14 byte long frame
// read timestamp
stream.Read(buffer, 2, 6);
nanosec = ((buffer[4] & 0x3f) << 24) |
(buffer[5] << 16) |
(buffer[6] << 8) |
(buffer[7]);
daysec = (buffer[2] << 10) |
(buffer[3] << 2) |
(buffer[4] >> 6);
timestamp = DateTime.Today.AddSeconds(daysec);
timestamp = timestamp.AddMilliseconds(nanosec / 1000);
// plausibility check
if (Math.Abs((DateTime.Now - timestamp).Seconds) > 10)
{
// time difference > 10sec --> discard timestamp
timestamp = DateTime.UtcNow;
}
// read signal strength
stream.Read(buffer, 8, 1);
signal_strength = buffer[8];
// read frame
stream.Read(buffer, 9, 14);
// convert to AVR string
RTL = BitConverter.ToString((byte[])buffer, 9, 14).Replace("-", String.Empty);
RTL = "*" + RTL + ";";
break;
default:
// false decode
RTL = null;
break;
}
}
// check for timeout 10sec
stop = DateTime.UtcNow;
if (stop - start > new TimeSpan(0, 0, 10))
{
throw new TimeoutException();
}
}
// while ((RTL == null) && !this.CancellationPending);
while (RTL == null);
if (RTL == null)
{
return(null);
}
RTLMessage msg = new RTLMessage();
msg.RawMessage = RTL;
msg.TimeStamp = timestamp;
msg.SignalStrength = signal_strength;
return(msg);
}
private void bw_Receiver_DoWork(object sender, DoWorkEventArgs e)
{
Thread.CurrentThread.Priority = ThreadPriority.Highest;
StreamReader sr = null;
TcpClient client = null;
RTLMessage msg = null;
// outer loop
do
{
try
{
// setup TCP listener
client = new TcpClient();
string server = Settings.Server;
client.Connect(server, Settings.Port);
sr = new StreamReader(client.GetStream());
// inner loop
// receive messages in a loop
do
{
if (Settings.Binary)
{
msg = ReceiveBinaryMsg(sr.BaseStream);
}
else
{
msg = ReceiveAVRMsg(sr);
}
// decode the message
if (msg.RawMessage.StartsWith("*") && msg.RawMessage.EndsWith(";"))
{
// try to decode the message
string info = "";
try
{
Console.Write("[" + this.GetType().Name + "]: " + msg.RawMessage + "-- > ");
info = Decoder.DecodeMessage(msg.RawMessage, msg.TimeStamp);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
Console.WriteLine(info);
}
}while ((msg != null) && !bw_Receciver.CancellationPending);
}
catch (Exception ex)
{
// report error
Console.WriteLine("Error reading from TCP connection: " + ex.Message);
// wait 10 sec
int i = 0;
while ((i < 10) && !bw_Receciver.CancellationPending)
{
Thread.Sleep(1000);
i++;
}
}
finally
{
// try to close the stream and TCP client
try
{
if (sr != null)
{
sr.Close();
}
}
catch
{
}
try
{
if (client != null)
{
client.Close();
}
}
catch
{
}
}
}while (!bw_Receciver.CancellationPending);
}
