Flutter连接PostgreSQL遇连接拒绝错误，请求解决方案

问题代码 #

import 'package:postgres/postgres.dart';

void main() async {
  final conn = PostgreSQLConnection(
    'localhost',
    5432,
    'trackerapp',
    username: 'jax',
    password: '',
  );

  await conn.open();
  print('succes');

  // query 

  await conn.close();
  print('connection close');
}

报错信息 #

E/flutter ( 7000): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: SocketException: Connection refused (OS Error: Connection refused, errno = 111), address = localhost, port = 49389
E/flutter ( 7000): #0 _NativeSocket.startConnect (dart:io-patch/socket_patch.dart:694:35)
E/flutter ( 7000): #1 _NativeSocket.connect (dart:io-patch/socket_patch.dart:960:12)
E/flutter ( 7000): #2 _RawSocket.connect (dart:io-patch/socket_patch.dart:1843:26)
E/flutter ( 7000): #3 RawSocket.connect (dart:io-patch/socket_patch.dart:21:23)
E/flutter ( 7000): #4 Socket._connect (dart:io-patch/socket_patch.dart:2068:22)
E/flutter ( 7000): #5 Socket.connect (dart:io/socket.dart:747:21)
E/flutter ( 7000): #6 PostgreSQLConnection.open (package:postgres/src/connection.dart:189:32)
E/flutter ( 7000): #7 main (package:app1/main.dart:12:14)
E/flutter ( 7000): #8 _runMain.<anonymous closure> (dart:ui/hooks.dart:131:23)
E/flutter ( 7000): #9 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19)
E/flutter ( 7000): #10 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:26)

解决步骤 #

• 确认PostgreSQL服务正在运行

  • Linux：执行sudo systemctl status postgresql查看状态，未运行则用sudo systemctl start postgresql启动
  • Windows：打开服务管理器（services.msc），找到PostgreSQL服务，确保状态为“正在运行”
  • Mac：执行brew services list查看，未运行则用brew services start postgresql启动

• 替换localhost为适配模拟器/真机的地址

  • Android模拟器：将'localhost'改为'10.0.2.2'（模拟器专属回环地址，映射宿主机的localhost）
  • iOS模拟器：可直接用'localhost'，但真机需替换为宿主机的局域网IP（如192.168.1.100）
  • 修改后的连接示例：

    final conn = PostgreSQLConnection(
      '10.0.2.2',
      5432,
      'trackerapp',
      username: 'jax',
      password: '',
    );
    

• 修改PostgreSQL监听配置

  1. 找到postgresql.conf配置文件（路径：Linux /var/lib/postgresql/<版本>/main/，Windows C:\Program Files\PostgreSQL\<版本>\data\，Mac /usr/local/var/postgres/）
  2. 修改listen_addresses = '*'（允许所有IP访问，开发环境适用）
  3. 重启PostgreSQL服务使配置生效

• 配置pg_hba.conf开放访问权限

  1. 打开同目录下的pg_hba.conf文件
  2. 添加访问规则，例如允许用户jax从任意IP连接数据库trackerapp：

     host    trackerapp     jax             0.0.0.0/0               scram-sha-256
     

     本地开发也可简化为：

     host    trackerapp     jax             127.0.0.1/32            trust
     

  3. 重启PostgreSQL服务

• 检查防火墙设置

  • Linux：执行sudo ufw allow 5432开放5432端口
  • Windows：在Windows Defender防火墙中添加入站规则，允许PostgreSQL服务或5432端口的连接
  • Mac：在系统设置-网络-防火墙中，允许PostgreSQL的网络访问

内容的提问来源于stack exchange，提问作者Janarbek Keneshbekov