Flutter真机无法与Flask服务器通信（CSV上传接口）的排查求助

背景信息 #

• Flask服务器：运行于虚拟环境，提供/predict/plotPOST接口接收CSV文件，返回基于CSV数据生成的base64编码图片字符串。
• Flutter应用：通过文件选择器选取CSV文件，上传至Flask接口，解码后展示返回的图片。

相关代码 #

Flutter代码（uploadCSV函数） #

var dio = Dio();
FilePickerResult? result = await FilePicker.platform.pickFiles();
if (result != null) {
  File file = File(result.files.single.path ?? " ");
  String fileName = file.path.split('/').last;
  String filePath = file.path;
  FormData data = FormData.fromMap(
      {'file': await MultipartFile.fromFile(filePath, filename: fileName)});
  try {
    var response = await dio.post("http://10.0.2.2:5000/predict/plot",
        data: data, onSendProgress: (int sent, int total) {
      print('$sent  $total');
    });
    _imagebase64 = jsonDecode(response.toString())['image'];
  } catch (e) {
    print(e.toString());
  }
} else {
  print("Response is null");
}

服务端代码（Flask app） #

import joblib
import ast
from io import BytesIO
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import base64
from flask import Flask, request, jsonify

app = Flask(__name__)

plt.switch_backend('Agg')
@app.route('/predict/plot', methods=['POST'])
def plot():
    if 'file' not in request.files:
        obj = {"status": "fail", "message": 'No file part'}
        return jsonify(obj)

    file = request.files['file']

    # Validate file type
    if file.filename.endswith('.csv'):
        # Process CSV data
        df = pd.read_csv(file)
        # Create a simple plot
        data = df['Diseases']
        column_data = {}
        #plot
        for row in data:
                value = row[0]
                if value in column_data:
                    column_data[value] += 1
                else:
                    column_data[value] = 1

            # Generate a bar chart
        categories = list(column_data.keys())
        counts = list(column_data.values())

        plt.bar(categories, counts)
        plt.xlabel('Categories')
        plt.ylabel('Count')
        plt.title('Bar Chart')

        # Convert the plot to a base64-encoded image
        plot_image_base64 = plot_to_base64(plt)

        # Close the plot to release resources
        plt.close()

        # Return the base64-encoded image as part of the JSON response
        obj = {"status": "success", "location": df.loc[0, 'Location'], "image": plot_image_base64}
        print(obj)
        return jsonify(obj)
    else:
        obj = {"status": "fail", "message": 'Invalid file type. Please upload a CSV file'}
        return jsonify(obj)

def plot_to_base64(plt_obj):
    # Save the plot to a BytesIO object
    plot_bytes = BytesIO()
    plt_obj.savefig(plot_bytes, format='png')
    plot_bytes.seek(0)

    # Convert the plot to a base64-encoded image
    plot_base64 = base64.b64encode(plot_bytes.read()).decode('utf-8')
    return plot_base64

if __name__ == "__main__":
  app.run(host='0.0.0.0', port=5000)

已尝试操作 #

将Flutter应用中的请求地址修改为PC的IP地址，但出现“connection timed out”和“socket exception”错误。

请求协助 #

• 排查连接失败的根本原因
• 验证网络连通性与防火墙设置
• 配置必要的CORS
• 完善Flutter应用的错误处理
• 提供额外调试策略

可提供设备环境、完整错误日志等补充信息。

内容的提问来源于stack exchange，提问作者Saurav Haldar