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: (){},),

          ],

        ),

      ),

    );

  }

}