private void ReceiveEnd(IAsyncResult ar)
{
// Retrieve state
var state = (ConnectionState)ar.AsyncState;
// Complete read
Int32 chunkLength;
try {
chunkLength = state.Connection.EndReceive(ar);
} catch (ObjectDisposedException) // Occurs during in-flight disposal - we need to catch it for a graceful shutdown
{
return; // Abort read
} catch (SocketException ex) // Occurs when there is a connection error
{
// Report error
RaiseDeviceError(state, ex.Message, false);
return; // Abort receive
}
// If the expected number of bytes hasn't arrived yet, wait for more bytes
if (state.ReceiveBufferExpected != state.ReceiveBufferUsed)
{
// Receive more bytes
ReceiveStart(state);
return;
}
// If header hasn't been processed yet, process it
if (null == state.ReceiveReceiveMessageType)
{
// Yes, this could have been in the switch below, but it made for some funky reading
// Check sync bytes
if (state.ReceiveBuffer[0] != 0x02 || state.ReceiveBuffer[1] != 0x55)
{
RaiseDeviceError(state, $"Incorrect sync bytes encountered ({state.ReceiveBuffer[0]},{state.ReceiveBuffer[1]}).", true);
return;
}
// Decode message type
state.ReceiveReceiveMessageType = (ReceiveMessageTypes)state.ReceiveBuffer[2];
// Decode message length and increase the number of bytes expected
var messageLength = BitConverter.ToUInt16(state.ReceiveBuffer, 3);
state.ReceiveBufferExpected += messageLength;
// Receive more bytes
ReceiveStart(state);
return;
}
switch (state.ReceiveReceiveMessageType.Value)
{
case ReceiveMessageTypes.Hello: // Device is providing basic information about it
state.Device = Device.Parse(state.ReceiveBuffer, 5);
state.Connection.Send(new Byte[] { 0x02, 0x55 }); // Sync bytes
state.Connection.Send((Byte)TransmitMessageTypes.HelloResponse); // Message type
state.Connection.Send((UInt16)8); // Message length
state.Connection.Send(TelematicsTime.Encode(DateTime.UtcNow)); // Time
state.Connection.Send((UInt32)0); // Flags TODO: how to tell device to redirect to OEM?
OnDeviceConnected?.Invoke(this, new OnDeviceConnectedArgs()
{
RemoteAddressString = state.RemoteAddressString,
Device = state.Device
});
break;
case ReceiveMessageTypes.Records: // Device is providing records
// It seems that MESSAGE contains multiple RECORDS
// which contain multiple FIELDS
// which contains multiple things which I'm going to call ATTRIBUTES
// Attributes are the actual data.
//
// In summary: MESSAGE => RECORDS => FIELDS => ATTRIBUTES
var position = 5;
var records = new List <Record>();
while (position < state.ReceiveBufferExpected)
{
records.Add(Record.Parse(state.ReceiveBuffer, ref position));
}
OnRecordsReceived?.Invoke(this, new OnRecordsReceivedArgs()
{
RemoteAddressString = state.RemoteAddressString,
Device = state.Device,
Records = records
});
break;
case ReceiveMessageTypes.CommitRequest: // Device asking us to confirm that we've successfully received and stored records
// Send confirmation // TODO: When would we not confirm a commit?
state.Connection.Send(new Byte[] { 0x02, 0x55 }); // Sync bytes
state.Connection.Send((Byte)TransmitMessageTypes.CommitResponse); // Message type
state.Connection.Send((UInt16)1); // Message length
state.Connection.Send((Byte)1); // Success
break;
case ReceiveMessageTypes.VersionData: // Device providing version information (no idea what this is for!!)
RaiseDeviceError(state, $"Version information received and discarded.", false); // TODO: do something with the information
break;
case ReceiveMessageTypes.TimeRequest: // Device asking for the current time
state.Connection.Send(new Byte[] { 0x02, 0x55 }); // Sync bytes
state.Connection.Send((Byte)TransmitMessageTypes.TimeResponse); // Message type
state.Connection.Send((UInt16)4); // Message length
state.Connection.Send(TelematicsTime.Encode(DateTime.UtcNow)); // Current time
break;
case ReceiveMessageTypes.AsyncMessageResponse: // Device is giving responses to async messages, which is not currently implemented, so should not be recieved
RaiseDeviceError(state, $"Message async responses received and discarded.", false); // TODO: do something with the information
break;
default:
RaiseDeviceError(state, $"Unsupported message type received ({state.ReceiveReceiveMessageType.Value}). Message discarded.", false);
break;
}
// Receive more
ResetState(state);
ReceiveStart(state);
}
public void DecodeOne()
{
Assert.Equal(new DateTime(2013, 01, 01, 0, 0, 1, DateTimeKind.Utc), TelematicsTime.Decode(1));
}
public void EncodeZero()
{
Assert.Equal((UInt32)0, TelematicsTime.Encode(new DateTime(2013, 01, 01, 0, 0, 0, DateTimeKind.Utc)));
}
public void DecodeZero()
{
Assert.Equal(new DateTime(2013, 01, 01, 0, 0, 0, DateTimeKind.Utc), TelematicsTime.Decode(0));
}