引入插件 ：web_socket_channel: ^3.0.1
使用如下代码：
class _MyHomePageState extends State<MyHomePage> {String text = "";var textController = TextEditingController();late IOWebSocketChannel channel;void _incrementCounter() {channel.sink.add(textController.text);textController.text = "";}@overridevoid initState() {super.initState();}@overrideWidget build(BuildContext context) {HttpClient httpClient = HttpClient();/// 解决证书问题httpClient.badCertificateCallback = (X509Certificate cert, String host, int port) {// String PEM = "XXXXXX";// 证书信息// if(cert.pem == PEM){// return true;// 正式一致，则允许发送数据// }// return false;/// 这里可写死truereturn true;};channel = IOWebSocketChannel.connect(Uri.parse('ws://echo.websocket.org'), customClient: httpClient);return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text("WebSocket例子"),),body: StreamBuilder(stream: channel.stream,builder: (context, snapshot) {if (snapshot.connectionState == ConnectionState.active) {text = "${snapshot.data}";} else if (snapshot.connectionState == ConnectionState.done) {text = "已断开连接，断开原因：${snapshot.error}";} else if (snapshot.connectionState == ConnectionState.waiting) {text = "连接中";} else {text = "...";}return Column(children: [Text(text),TextField(controller: textController,),TextButton(onPressed: () {channel.sink.close();},child: const Text("断开")),TextButton(onPressed: () {setState(() {});},child: const Text("重连")),],);}),floatingActionButton: FloatingActionButton(onPressed: _incrementCounter,tooltip: 'Increment',child: const Icon(Icons.add),),);}
}