Dart编写一个TCP客户端Flutter界面程序

以下是一个使用Dart编写的TCP客户端Flutter界面程序的示例：

import 'dart:convert';
import 'dart:io';

import 'package:flutter/material.dart';

class TcpClient extends StatefulWidget {
  @override
  _TcpClientState createState() => _TcpClientState();
}

class _TcpClientState extends State<TcpClient> {
  final TextEditingController _hostController = TextEditingController();
  final TextEditingController _portController = TextEditingController();
  final TextEditingController _messageController = TextEditingController();
  Socket? _socket;

  void _connect() async {
    try {
      final host = _hostController.text;
      final port = int.parse(_portController.text);
      _socket = await Socket.connect(host, port);
      setState(() {});
    } catch (e) {
      print('Error: $e');
    }
  }

  void _sendMessage() {
    final message = _messageController.text;
    _socket?.write(message);
    _messageController.clear();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TCP Client'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            TextField(
              controller: _hostController,
              decoration: InputDecoration(
                labelText: 'Host',
              ),
            ),
            SizedBox(height: 8),
            TextField(
              controller: _portController,
              decoration: InputDecoration(
                labelText: 'Port',
              ),
            ),
            SizedBox(height: 16),
            ElevatedButton(
              onPressed: _connect,
              child: Text('Connect'),
            ),
            SizedBox(height: 16),
            if (_socket != null)
              Expanded(
                child: StreamBuilder(
                  stream: _socket!.transform(utf8.decoder),
                  builder: (context, snapshot) {
                    if (snapshot.hasData) {
                      return SingleChildScrollView(
                        child: Text(snapshot.data.toString()),
                      );
                    } else {
                      return Center(
                        child: CircularProgressIndicator(),
                      );
                    }
                  },
                ),
              ),
            SizedBox(height: 16),
            if (_socket != null)
              TextField(
                controller: _messageController,
                decoration: InputDecoration(
                  labelText: 'Message',
                ),
              ),
            SizedBox(height: 8),
            if (_socket != null)
              ElevatedButton(
                onPressed: _sendMessage,
                child: Text('Send'),
              ),
          ],
        ),
      ),
    );
  }
}

在此示例中，我们使用 `Socket.connect` 方法连接到指定的主机和端口。我们还使用 `StreamBuilder` 将接收到的数据流转换为可读文本，并将其显示在屏幕上。最后，我们还实现了一个发送消息的方法，该方法将文本框中的消息写入到套接字中。