public async Task <Result> ReadVariable(string pVarName)
{
Result result = new Result();
// Read Variable request packet structure example:
// 0 1 2 3 4 5 6
// xx xx | 00 0A | 00 | 00 07 | 24 4F 56 5F 50 52 4F
// | 10 | 0 | 7 | $ O V _ P R O
// REQ ID | REQ LEN | READ=00 | VAR NAME LEN | VAR NAME CHARS
// (RANDOM)|
if (pVarName.Length == 0)
{
result.ErrorMessage = "No variable was written";
return(result);
}
var PKT_var_name = new byte[pVarName.Length];
PKT_var_name = Encoding.UTF8.GetBytes(pVarName);
var PKT_name_length = new byte[2];
PKT_name_length[0] = (byte)((pVarName.Length >> 8) & 255);
PKT_name_length[1] = (byte)(pVarName.Length & 255);
byte PKT_mode_is_read = 0;
var PKT_req_len = new byte[2];
PKT_req_len[0] = (byte)(((pVarName.Length + 3) >> 8) & 255);
PKT_req_len[1] = (byte)((pVarName.Length + 3) & 255);
var PKT_req_id = new byte[2];
PKT_req_id[0] = (byte)((_msgID >> 8) & 255);
PKT_req_id[1] = (byte)(_msgID & 255);
_msgID++;
if (_msgID > _lastID)
{
_msgID = _firstID;
}
var REQ_packet = new byte[pVarName.Length + 7 + 1];
REQ_packet[0] = PKT_req_id[0];
REQ_packet[1] = PKT_req_id[1];
REQ_packet[2] = PKT_req_len[0];
REQ_packet[3] = PKT_req_len[1];
REQ_packet[4] = PKT_mode_is_read;
REQ_packet[5] = PKT_name_length[0];
REQ_packet[6] = PKT_name_length[1];
PKT_var_name.CopyTo(REQ_packet, 7);
DataWriter writer;
using (writer = new DataWriter(_socket.OutputStream))
{
// Set the Unicode character encoding for the output stream
writer.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
// Specify the byte order of a stream.
writer.ByteOrder = ByteOrder.LittleEndian;
// Gets the size of UTF-8 string.
writer.MeasureString(Encoding.UTF8.GetString(REQ_packet));
// Write a string value to the output stream.
writer.WriteBytes(REQ_packet);
// Send the contents of the writer to the backing stream.
try
{
await writer.StoreAsync();
await writer.FlushAsync();
}
catch (Exception ex)
{
SocketErrorStatus webErrorStatus = Windows.Networking.Sockets.SocketError.GetStatus(ex.GetBaseException().HResult);
result.ErrorMessage = (webErrorStatus.ToString() != "Unknown" ? webErrorStatus.ToString() : ex.Message);
return(result);
}
// In order to prolong the lifetime of the stream, detach it from the DataWriter
writer.DetachStream();
}
// Read Variable response packet structure example:
// 0 1 2 3 4 5 6
// xx xx | 00 0A | 00 | 00 06 | 35 35 33 39 39 33 | 00 01 01
// | 10 | 0 | 6 | 5 5 3 9 9 3 | 0 1 1
// SAME AS| RSP LEN | READ=00 | VALUE LEN | VALUE CHARS | TRAILER
// REQUEST|
DataReader reader;
ByteBuilder byteBuilder = new ByteBuilder();
using (reader = new DataReader(_socket.InputStream))
{
// Read the length of the payload that will be received.
reader.InputStreamOptions = InputStreamOptions.Partial;
// The encoding and byte order need to match the settings of the writer we previously used.
reader.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
reader.ByteOrder = ByteOrder.LittleEndian;
// Send the contents of the writer to the backing stream.
// Get the size of the buffer that has not been read.
try
{
do
{
await reader.LoadAsync(_readBuffer);
var bytes = new Byte[reader.UnconsumedBufferLength];
reader.ReadBytes(bytes);
byteBuilder.AppendBytes(bytes);
// Keep reading until we consume the complete stream.
}while (reader.UnconsumedBufferLength > 0);
}
catch (Exception ex)
{
SocketErrorStatus webErrorStatus = SocketError.GetStatus(ex.GetBaseException().HResult);
result.ErrorMessage = (webErrorStatus.ToString() != "Unknown" ? webErrorStatus.ToString() : ex.Message);
return(result);
}
finally
{
reader.DetachStream();
}
}
var flattenedList = byteBuilder._bytes.SelectMany(bytes => bytes);
var RSP_packet = flattenedList.ToArray();
try
{
int RSP_len = (RSP_packet[2] << 8) | RSP_packet[3];
int RSP_val_len = (RSP_packet[5] << 8) | RSP_packet[6];
result.Data = Encoding.ASCII.GetString(RSP_packet, 7, RSP_val_len);
int RSP_read_status = RSP_packet[7 + (RSP_val_len + 2)];
if ((RSP_read_status > 0) & (RSP_val_len > 0) &
(RSP_packet[0] == PKT_req_id[0]) & (RSP_packet[1] == PKT_req_id[1]))
{
result.Succeeded = true;
return(result);
}
else
{
result.ErrorMessage = "Cannot be read";
return(result);
}
}
catch (Exception ex)
{
result.ErrorMessage = ex.Message;
return(result);
}
}