Flutter send json to websocket server as bytes?

Question

I have a JSON like message like this:

  static getHiMsg(String token, String sender) {
   var msg = {
        "token": token,
        "user_addr": sender,
        "ua": "dart/fluter-v0.0.1",
        "device": "Phone",
        "location": "Hunan"
    };
    var outMsg = {
        "msg_type": "hi",
        "payload": msg
    };
    return outMsg;
  }

and I wanna send this message to websocket server which only deal with json request, if a plain text or wrong format json, it will refuse connection.

Here is what am doing:

  void _sayHi() async {
    _token = await _prefs.getToken();
    _userAddr = await _prefs.getUserAddr();
    var hi = getHiMsg(_token, _userAddr);
      print(hi);
      channel.sink.add(hi);
  }

channel is just IOWebSocketChannel.connect(wsUrl) Here my server just can not get the right JSON format request, actually this is the right logic in Python:

def hi_msg(token, addr):
# change this to one account token and user_addr
msg = {
    "token": token,
    "user_addr": addr,
    "ua": "py/macos",
    "device": "mac",
    "location": "Hunan"
}
out_msg = {
    "msg_type": "hi",
    "payload": msg
}
msg_str = json.dumps(out_msg)
b = bytes(msg_str, 'utf-8')
return b

How to achieve this in Dart and Flutter? I am not quite familiar with Dart bytes operation.

Answer 1

You can get a JSON string in Dart

import 'dart:convert';

...

var jsonString = json.encode(data);

and get bytes of the string using

var bytes = jsonString.codeUnits;