Sounds like you are having an issue with correct string encoding. You are receiving binary data which can be a problem.
It looks as though you may be getting data but not being interpreted correctly. you may try using the following line of code using the iso-8859-1 Western European (ISO) encoding. I use this encoding with good success. I've also used (1252) as well for binary data.
string strData = Encoding.GetEncoding(28591).GetString(buffer, 0, buffer.Length);
Without seeing your code it is difficult to know where the issue lies, it may well be that if you are treating the values as string they may well be being converted to their ascii equivalents, In that case, using the same encoding I would pass these values into an int or Byte array for proper interpretation.
Good luck.