catch socket error

whois_handler.dart

import 'dart:io';
import 'package:async/async.dart';
import 'dart:convert';

class Whois{
  Whois({this.domain});

  Socket socket;
  String domain;

  bool dataFinished = false;
  bool doneFinished = false;
  bool errorFinished = false;
  bool saveFinished = false;
  bool getData = false;

  int tryTimes = 0;
  int tryDone = 0;
  int errorTime = 0;

  String rawWhois = '';

  Future request()async{
    dataFinished = false;
    doneFinished = false;
    errorFinished = false;
    saveFinished = false;
    getData = false;

    try {
      socket = await Socket.connect('whois.cnnic.net.cn', 43);
      socket.listen(onData, onError: onError);
      socket.write(domain + '\n');
    }catch(e){
      print('0, create socket error: ${e.toString()}');
    }

    try{
      await socket.done;
      print('4. $domain done');
    }catch(error){
      print('1, transit error: ${error.toString()}');
      await Future.delayed(Duration(seconds: 2));
      await request();
    }
  }

  void onData(value)async {
    getData = true;
    rawWhois = utf8.decode(value);
    print('3. whois: $rawWhois}');
    saveFinished = true;
    print('mmmmmmmmmmmmmmmmmmmmmmm       $domain done      mmmmmmmmmmmmmmmmmmmmmmmm');
  }

  void onError(e)async{
    socket.destroy();
    print('error: ${e.toString()}');

    if(errorTime<2){
      await Future.delayed(Duration(seconds: 2));
      request();
      errorTime++;
    }else{
      print('5. try too many times but failed, force to next');
      saveFinished = true;
    }
  }

}

　　

main.dart

import 'package:flutter/material.dart';
import 'package:spatialhash/spatialhash.dart';
import 'utils/whois_handler.dart';
import 'dart:async';

main()=>runApp(MaterialApp(
  home: MyApp(),
));

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  List a = 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  checkWhois()async{
    for(int i=0; i<a.length; i++){
      var x = Whois(domain: a[i]);
      x.request();
      while(!x.saveFinished){
        await Future.delayed(Duration(milliseconds: 100));
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('ab'),),
      body: Container(
        width: double.infinity, height: double.infinity,
        child: Column(
          children: <Widget>[
            RaisedButton(child: Text('check'),onPressed: (){
              checkWhois();
            },),
            RaisedButton(child: Text('stop'),onPressed: (){},),
          ],
        ),
      ),
    );
  }
}