参考如下方法：

首先使用full-sdk,可以在我司百度网盘下载

import ethernet from '@ohos.net.ethernet'
onCreate(want, launchParam) {
  let InterfaceConfiguration: ethernet.InterfaceConfiguration = {
    mode: ethernet.IPSetMode.STATIC,
    ipAddr: "192.168.0.2",
    route: "192.168.0.1",
    gateway: "192.168.0.1",
    netMask: "255.255.255.0",
    dnsServers: "8.8.8.8",
  }

  try {
    ethernet.setIfaceConfig("eth0", InterfaceConfiguration).then(() => {
      console.log("setIfaceConfig promiss ok ");
    }).catch((error) => {
      console.error("setIfaceConfig promiss error = " + error);
    });
  } catch (err) {
    console.error("error = " + err);
  }
}

module.json5增加权限：

"requestPermissions": [
  {
    "name": "ohos.permission.CONNECTIVITY_INTERNAL",
    "reason": "$string:reason",
    "usedScene": {
      "abilities": [
        "FormAbility"
      ],
      "when": "inuse"
    }
  }
]

修改系统签名：

SDK_PATH/toolchains\lib\UnsgnedReleasedProfileTemplate.json

删除掉当前签名文件：C:\Users\xxx.ohos\config\openharmony\

再重新签名即可

注：设置为静态IP，只能局域网访问网络，外网不通

api参考:

https://gitee.com/openharmony/docs/blob/master/zh-cn/application-dev/reference/apis/js-apis-net-ethernet.md#ohosnetethernet-%E4%BB%A5%E5%A4%AA%E7%BD%91%E8%BF%9E%E6%8E%A5%E7%AE%A1%E7%90%86