HarmonyOS 鸿蒙Next 使用Remote Communication Kit（远场通信服务）下载文件一直失败

Succeeded in getting the response null 是下载文件成功的信息，下载文件成功代码如下：

import { fileIo } from '[@kit](/user/kit).CoreFileKit';
import { rcp } from '[@kit](/user/kit).RemoteCommunicationKit';
import { BusinessError } from '[@kit](/user/kit).BasicServicesKit';

[@Entry](/user/Entry)
[@Component](/user/Component)
struct LocationPage1 {
 [@State](/user/State) message: string = '点击此处下载文件';

 async testRcp1() {
   let downloadToFile: rcp.DownloadToFile = {
     kind: 'file',
     file: fileIo.openSync(getContext(this).tempDir + '/demo.zip',
       fileIo.OpenMode.READ_WRITE | fileIo.OpenMode.CREATE) //请根据自身业务选择合适的路径
   } as rcp.DownloadToFile

   console.log('getContext(this).tempDir为：' + getContext(this).tempDir)
   const session = rcp.createSession();
   session.downloadToFile("http://10.84.18.60:3000/download", downloadToFile).then((response) => {
     console.info(`Succeeded in getting the response ${response}`);
   }).catch((err: BusinessError) => {
     console.error(`DownloadToFile failed, the error message is ${JSON.stringify(err)}`);
   });
 }

 build() {
   RelativeContainer() {
     Text(this.message)
       .id('LocationPage1HelloWorld')
       .fontSize(50)
       .fontWeight(FontWeight.Bold)
       .alignRules({
         center: { anchor: '__container__', align: VerticalAlign.Center },
         middle: { anchor: '__container__', align: HorizontalAlign.Center }
       })
       .onClick(() => {
         this.testRcp1()
       })
   }
   .height('100%')
   .width('100%')
 }
}