Error: as shown in the following figure

After many ideological struggles, he began to solve the problem after admitting that it was his own problem:

{
  "apiUrl": "http://192.168.56.101:5000/",
  "port":  "8080",
  "host": "127.0.0.1",
  "socketHost": "172.16.0.26:443"//Add this line to the json file to configure public (no comments can be written in the json)
}

In reference https://github.com/vuejs/vue-cli/issues/1472

After the discussion, the following solutions are found:

webpack.dev.conf.js file:

Import

const URL = require('../static/config.json');
const socketHost = URL.socketHost;

Add content in devServer: {}:

public: socketHost,
disableHostCheck: true

Fortunately, the problem is solved!