How do I get the value through streambuilder?

Question

Language : Dart(Flutter)

Problem : Unable to get value to Streambuilder

Hello, Real-time data received via restapi through a web socket. And I wanted to show the received data in real time on the app screen I used Streambuilder and the snapshot went null. What should I do? Advice is welcome.

// home_screen.dart (Files to Run)
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:kis/services/domestic_fo/real_time/future_hoka.dart';

class HomeScreen extends StatelessWidget {
  HomeScreen({super.key});

  Stream realfuture = realFutureHoka();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: StreamBuilder(
        stream: realfuture,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return Text('${snapshot.data}');
            // I want is this line
          }
          return Center(child: CircularProgressIndicator());
          // but result this line
        },
      ),
      backgroundColor: Colors.white,
    );
  }
}

i can receive the value through the WebSocket channel.print result type is String No problem until streambuilder was used

// future_hoka.dart (Data Files Received by WebSocket)
Stream realFutureHoka() async* {
  final channel = WebSocketChannel.connect(
      Uri.parse("ws://ops.koreainvestment.com:21000/tryitout/H0IFASP0"));
  await channel.ready;
  channel.sink.add(
    jsonEncode(
      {
        "header": {
          "appkey": appkey,
          "appsecret": appsecret,
          'custtype': 'P',
          'tr_type': '1',
          'content-type': 'utf-8'
        },
        "body": {
          "input": {"tr_id": "H0IFASP0", "tr_key": FUTURE_CODE}
        }
      },
    ),
  );
  channel.stream.listen(
    (data) {
      print(data);
      return data;
    },
  );
}