拒绝连接到“ws://localhost:3000/cpp”,因为它违反了以下内容安全策略指令:

WebpackPluginRenderConfig

/**
     * Sets the [`Content-Security-Policy` header](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy)
     * for the Webpack development server.
     *
     * Normally you would want to only specify this as a `<meta>` tag. However, in development mode,
     * the Webpack plugin uses the `devtool: eval-source-map` source map setting for efficiency
     * purposes. This requires the `'unsafe-eval'` source for the `script-src` directive that wouldn't
     * normally be recommended to use. If this value is set, make sure that you keep this
     * directive-source pair intact if you want to use source maps.
     *
     * Default: `default-src 'self' 'unsafe-inline' data:;`
     * `script-src 'self' 'unsafe-eval' 'unsafe-inline' data:`
     */
    devContentSecurityPolicy?: string;

所以这应该可以解决问题

 plugins: [
        [
          "@electron-forge/plugin-webpack",
          {
            devServer: {
              allowedHosts: 'auto'
            },
            devContentSecurityPolicy: "connect-src 'self' ws://localhost:3000/cpp 'unsafe-eval'",
    
             // rest of config 
        ]
      ]