鸿蒙网络编程系列 2-UDP 回声服务器的实现

2024-10-22
广东
本文字数：2782 字
阅读完需：约 9 分钟

1.回声服务器简介

回声服务器指的是这样一种服务器，它接受客户端的连接，并且把收到的数据原样返回给客户端，本文将使用 UDP 协议实现一个回声服务器，关于 UDP 通讯相关方法的介绍可以参考上一篇博文：鸿蒙网络编程系列1-UDP通讯示例，最终应用的界面如下图所示：

2.实现思路

首先创建一个 UDP 实例，然后绑定到指定的端口，再订阅 message 事件，在处理该事件的时候，输出接收到的消息并且把该消息通过 send 方法发回客户端。

3.实现步骤

步骤 1：创建 Empty Ability 项目。

步骤 2：在 module.json5 配置文件加上对权限的声明：

"requestPermissions": [
{
"name": "ohos.permission.INTERNET"
},
{
"name": "ohos.permission.GET_WIFI_INFO"
}
]

这里分别添加了访问互联网和访问 WIFI 信息的权限。

步骤 3：在 Index.ets 文件里添加如下的代码：

import socket from '@ohos.net.socket';import wifiManager from '@ohos.wifiManager';import systemDateTime from '@ohos.systemDateTime';import util from '@ohos.util';import hilog from '@ohos.hilog';
//执行UDP通讯的对象let udpSocket = socket.constructUDPSocketInstance();
//说明：本地的IP地址不是必须知道的，绑定时绑定到IP：0.0.0.0即可，显示本地IP地址的目的是方便对方发送信息过来//本地IP的数值形式let ipNum = wifiManager.getIpInfo().ipAddress//本地IP的字符串形式let localIp = (ipNum >>> 24) + '.' + (ipNum >> 16 & 0xFF) + '.' + (ipNum >> 8 & 0xFF) + '.' + (ipNum & 0xFF);
@Entry@Componentstruct Index {  //连接、通讯历史记录  @State msgHistory: string = ''  //本地端口  @State localPort: number = 9999  scroller: Scroller = new Scroller()
  build() {    Row() {      Column() {        Text("UDP回声服务器")          .fontSize(14)          .fontWeight(FontWeight.Bold)          .width('100%')          .textAlign(TextAlign.Center)          .padding(10)
        Flex({ justifyContent: FlexAlign.Start, alignItems: ItemAlign.Center }) {          Text("本地IP和端口：")            .width(100)            .fontSize(14)            .flexGrow(0)          Text(localIp)            .width(110)            .fontSize(14)            .flexGrow(0)          TextInput({ text: this.localPort.toString() })            .type(InputType.Number)            .onChange((value) => {              this.localPort = parseInt(value)            })            .width(80)            .flexGrow(3)
          Button("绑定")            .onClick(() => {              this.bind2Port()            })            .width(80)            .fontSize(14)            .flexGrow(0)
        }.width('100%')        .padding(10)
        Scroll(this.scroller) {          Text(this.msgHistory)            .textAlign(TextAlign.Start)            .padding(10)            .width('100%')            .backgroundColor(0xeeeeee)        }        .align(Alignment.Top)        .backgroundColor(0xeeeeee)        .height(300)        .flexGrow(1)        .scrollable(ScrollDirection.Vertical)        .scrollBar(BarState.On)        .scrollBarWidth(20)      }      .width('100%')      .justifyContent(FlexAlign.Start)      .height('100%')    }    .height('100%')  }
  //发送消息到目的ip和端口  sendMsg2Target(address: string, port: number, msg: string) {    //目的ip和端口    let remoteAddress = { address: address, port: port, family: 1 }    udpSocket.send({ data: msg, address: remoteAddress })      .then(async () => {        hilog.info(0x0000, 'sendMsg2Target', '%{public}s:%{public}d %{public}s',          remoteAddress.address, remoteAddress.port, msg)      })      .catch((e) => {        hilog.error(0x0000, 'sendMsg2Target', '%{public}s:%{public}d %{public}s',          remoteAddress.address, remoteAddress.port, e.message)      })  }
  //绑定本地端口  async bind2Port() {    //本地地址    let localAddress = { address: "0.0.0.0", port: this.localPort, family: 1 }
    await udpSocket.bind(localAddress)      .then(() => {        this.msgHistory = 'bind success' + "\r\n";      })      .catch((e) => {        this.msgHistory = 'bind fail' + e.message + "\r\n";      })
    //收到消息时的处理    udpSocket.on("message", async (value) => {      let msg = buf2String(value.message)      let remoteIP = value.remoteInfo.address      let remotePort = value.remoteInfo.port      //对端ip地址和端口的字符串形式      let remoteAddr = "[" + remoteIP + ":" + remotePort.toString() + "]:"      let time = await getCurrentTimeString()      this.msgHistory += remoteAddr + msg + time + "\r\n"      this.scroller.scrollEdge(Edge.Bottom)
      //把收到的消息发回发送方      this.sendMsg2Target(remoteIP, remotePort, msg)    })  }}
//同步获取当前时间的字符串形式async function getCurrentTimeString() {  let time = ""  await  systemDateTime.getDate().then(    (date) => {      time = date.getHours().toString() + ":" + date.getMinutes().toString()      + ":" + date.getSeconds().toString()    }  )  return "[" + time + "]"}
//ArrayBuffer转utf8字符串function buf2String(buf: ArrayBuffer) {  let msgArray = new Uint8Array(buf);  let textDecoder = util.TextDecoder.create("utf-8");  return textDecoder.decodeWithStream(msgArray)}