How to read byte array data in Dart?

user_10065044 0
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connecting TCP Socket server and sending Request. and also Server sends the response in Byte array. How to read byte array data in dart.

Socket.connect('localhost', 8081)
  .then((socket) {
//Establish the onData, and onDone callbacks
socket.listen((data) {
  print(new String.fromCharCodes(data).trim()); //Here data is byte[]
  //How to read byte array data

},
    onDone: () {
      print("Done");
      // socket.destroy();

    },
    onError: (e) {
      print('Server error: $e');
    });
 socket.add([255, 12, 0, 11, 0, 9, 34, 82, 69, 70, 84, 65, 72, 73, 76]);
 });
}
dart flutter
2 Answers

It depends on with data type was encoded to bytes. Let's suppose it's String Then you can do it with dart:convert library.

import 'dart:convert' show utf8;

final decoded = utf8.decode(data);
user_29247000

It's pretty clear that there's a message structure in those bytes. You give two examples of messages:

[255, 12, 0, 11, 0, 9, 34, 82, 69, 70, 84, 65, 72, 73, 76]

and

[255, 20, 0, 11, 0, 0, 0, 15, 80, 82, 69, 77, 84, 65, 72, 73, 76, 45, 53, 53, 57, 55, 48]

Both start with 255, followed by what looks like two or three little endian 16 bit words (12 and 11) and (20, 11 and 0) followed by a string, who's length is encoded in a leading byte. If you are expected to inter-operate with another system, you really need the protocol spec.

Assuming I've guessed the structure correctly, this code 

main() {
  Uint8List input = Uint8List.fromList([
    255,
    20,
    0,
    11,
    0,
    0,
    0,
    15,
    80,
    82,
    69,
    77,
    84,
    65,
    72,
    73,
    76,
    45,
    53,
    53,
    57,
    55,
    48
  ]);

  ByteData bd = input.buffer.asByteData();
  print(bd.getUint16(1, Endian.little)); // print the first short
  print(bd.getUint16(3, Endian.little)); // and the second
  print(bd.getUint16(5, Endian.little)); // and the third
  int stringLength = input[7]; // get the length of the string
  print(utf8.decode(input.sublist(8, 8 + stringLength))); // decode the string
}

produces

20
11
0
PREMTAHIL-55970

as expected

user_95977060
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