# IPC与RPC通信开发指导

## 场景介绍

IPC/RPC的主要工作是让运行在不同进程的Proxy和Stub互相通信，包括Proxy和Stub运行在不同设备的情况。


## 接口说明

**表1** Native侧IPC接口

| 类/接口 | 方法 | 功能说明 |
| -------- | -------- | -------- |
| [IRemoteBroker](../reference/apis/js-apis-rpc.md#iremotebroker) | sptr<IRemoteObject> AsObject() | 返回通信对象。Stub端返回RemoteObject对象本身，Proxy端返回代理对象。 |
| IRemoteStub | virtual int OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply, MessageOption &option) | 请求处理方法，派生类需要重写该方法用来处理Proxy的请求并返回结果。 |
| IRemoteProxy |  | 业务的Pory类需要从IRemoteProxy类派生。 |


## 开发步骤

### **Native侧开发步骤**

1. 添加依赖

   SDK依赖：

   ```
   #ipc场景
   external_deps = [
     "ipc:ipc_single",
   ]

   #rpc场景
   external_deps = [
     "ipc:ipc_core",
   ]
   ```

   此外， IPC/RPC依赖的refbase实现在公共基础库下，请增加对utils的依赖：

   ```
   external_deps = [
     "c_utils:utils",
   ]
   ```

2. 定义IPC接口ITestAbility

   SA接口继承IPC基类接口IRemoteBroker，接口里定义描述符、业务函数和消息码，其中业务函数在Proxy端和Stub端都需要实现。

   ```c++
   #include "iremote_broker.h"

   //定义消息码
   const int TRANS_ID_PING_ABILITY = 5;

   const std::string DESCRIPTOR = "test.ITestAbility";

   class ITestAbility : public IRemoteBroker {
   public:
       // DECLARE_INTERFACE_DESCRIPTOR是必需的，入参需使用std::u16string；
       DECLARE_INTERFACE_DESCRIPTOR(to_utf16(DESCRIPTOR));
       virtual int TestPingAbility(const std::u16string &dummy) = 0; // 定义业务函数
   };
   ```

3. 定义和实现服务端TestAbilityStub

   该类是和IPC框架相关的实现，需要继承 IRemoteStub<ITestAbility>。Stub端作为接收请求的一端，需重写OnRemoteRequest方法用于接收客户端调用。

   ```c++
   #include "iability_test.h"
   #include "iremote_stub.h"

   class TestAbilityStub : public IRemoteStub<ITestAbility> {
   public:
       virtual int OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply, MessageOption &option) override;
       int TestPingAbility(const std::u16string &dummy) override;
    };

   int TestAbilityStub::OnRemoteRequest(uint32_t code,
       MessageParcel &data, MessageParcel &reply, MessageOption &option)
   {
       switch (code) {
           case TRANS_ID_PING_ABILITY: {
               std::u16string dummy = data.ReadString16();
               int result = TestPingAbility(dummy);
               reply.WriteInt32(result);
               return 0;
           }
           default:
               return IPCObjectStub::OnRemoteRequest(code, data, reply, option);
       }
   }
   ```

4. 定义服务端业务函数具体实现类TestAbility

   ```c++
   #include "iability_server_test.h"

   class TestAbility : public TestAbilityStub {
   public:
       int TestPingAbility(const std::u16string &dummy);
   }

   int TestAbility::TestPingAbility(const std::u16string &dummy) {
       return 0;
   }
   ```

5. 定义和实现客户端 TestAbilityProxy

   该类是Proxy端实现，继承IRemoteProxy&lt;ITestAbility&gt;，调用SendRequest接口向Stub端发送请求，对外暴露服务端提供的能力。

   ```c++
   #include "iability_test.h"
   #include "iremote_proxy.h"
   #include "iremote_object.h"

   class TestAbilityProxy : public IRemoteProxy<ITestAbility> {
   public:
       explicit TestAbilityProxy(const sptr<IRemoteObject> &impl);
       int TestPingAbility(const std::u16string &dummy) override;
   private:
       static inline BrokerDelegator<TestAbilityProxy> delegator_; // 方便后续使用iface_cast宏
   }

   TestAbilityProxy::TestAbilityProxy(const sptr<IRemoteObject> &impl)
       : IRemoteProxy<ITestAbility>(impl)
   {
   }

   int TestAbilityProxy::TestPingAbility(const std::u16string &dummy){
       MessageOption option;
       MessageParcel dataParcel, replyParcel;
       dataParcel.WriteString16(dummy);
       int error = Remote()->SendRequest(TRANS_ID_PING_ABILITY, dataParcel, replyParcel, option);
       int result = (error == ERR_NONE) ? replyParcel.ReadInt32() : -1;
       return result;
   }
   ```

6. SA注册与启动

   SA需要将自己的TestAbilityStub实例通过AddSystemAbility接口注册到SystemAbilityManager，设备内与分布式的注册参数不同。

   ```c++
   // 注册到本设备内
   auto samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
   samgr->AddSystemAbility(saId, new TestAbility());

   // 在组网场景下，会被同步到其他设备上
   auto samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
   ISystemAbilityManager::SAExtraProp saExtra;
   saExtra.isDistributed = true; // 设置为分布式SA
   int result = samgr->AddSystemAbility(saId, new TestAbility(), saExtra);
   ```

7. SA获取与调用

   通过SystemAbilityManager的GetSystemAbility方法可获取到对应SA的代理IRemoteObject，然后构造TestAbilityProxy即可。

   ```c++
   // 获取本设备内注册的SA的proxy
   sptr<ISystemAbilityManager> samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
   sptr<IRemoteObject> remoteObject = samgr->GetSystemAbility(saId);
   sptr<ITestAbility> testAbility = iface_cast<ITestAbility>(remoteObject); // 使用iface_cast宏转换成具体类型

   // 获取其他设备注册的SA的proxy
   sptr<ISystemAbilityManager> samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();

   // networkId是组网场景下对应设备的标识符，可以通过GetLocalNodeDeviceInfo获取
   sptr<IRemoteObject> remoteObject = samgr->GetSystemAbility(saId, networkId);
   sptr<TestAbilityProxy> proxy(new TestAbilityProxy(remoteObject)); // 直接构造具体Proxy
   ```

### **JS侧开发步骤**

1. 添加依赖

   ```ts
   import rpc from '@ohos.rpc';
   // 仅FA模型需要导入@ohos.ability.featureAbility
   // import featureAbility from "@ohos.ability.featureAbility";
   ```

   Stage模型需要获取context

   ```ts
   import UIAbility from '@ohos.app.ability.UIAbility';
   import Want from '@ohos.app.ability.Want';
   import AbilityConstant from '@ohos.app.ability.AbilityConstant';
   import window from '@ohos.window';

   export default class MainAbility extends UIAbility {
       onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
           console.log("[Demo] MainAbility onCreate");
           let context = this.context;
       }
       onDestroy() {
           console.log("[Demo] MainAbility onDestroy");
       }
       onWindowStageCreate(windowStage: window.WindowStage) {
           // Main window is created, set main page for this ability
           console.log("[Demo] MainAbility onWindowStageCreate");
       }
       onWindowStageDestroy() {
           // Main window is destroyed, release UI related resources
           console.log("[Demo] MainAbility onWindowStageDestroy");
       }
       onForeground() {
           // Ability has brought to foreground
           console.log("[Demo] MainAbility onForeground");
       }
       onBackground() {
           // Ability has back to background
           console.log("[Demo] MainAbility onBackground");
       }
   }
   ```

2. 绑定Ability

   首先，构造变量want，指定要绑定的Ability所在应用的包名、组件名，如果是跨设备的场景，还需要绑定目标设备NetworkId（组网场景下对应设备的标识符，可以使用deviceManager获取目标设备的NetworkId）；然后，构造变量connect，指定绑定成功、绑定失败、断开连接时的回调函数；最后，FA模型使用featureAbility提供的接口绑定Ability，Stage模型通过context获取服务后用提供的接口绑定Ability。

   ```ts
   // 仅FA模型需要导入@ohos.ability.featureAbility
   // import featureAbility from "@ohos.ability.featureAbility";
   import rpc from '@ohos.rpc';
   import Want from '@ohos.app.ability.Want';
   import common from '@ohos.app.ability.common';
   import deviceManager from '@ohos.distributedHardware.deviceManager';

   let proxy: rpc.RemoteProxy;
   let connectId: number;

   // 单个设备绑定Ability
   let want: Want = {
       // 包名和组件名写实际的值
       bundleName: "ohos.rpc.test.server",
       abilityName: "ohos.rpc.test.server.ServiceAbility",
   };
   let connect: common.ConnectOptions = {
       onConnect: (elementName, remote: rpc.RemoteProxy) => {
           proxy = remote;
       },
       onDisconnect: (elementName) => {
       },
       onFailed: () => {
           proxy;
       }
   };
   // FA模型使用此方法连接服务
   // connectId = featureAbility.connectAbility(want, connect);

   connectId = this.context.connectServiceExtensionAbility(want,connect);

   // 跨设备绑定
   // 第一个参数是本应用的包名，第二个参数是接收deviceManager的回调函数
   deviceManager.createDeviceManager("ohos.rpc.test", (err: Error, data: deviceManager.DeviceManager) => {
     if (err) {
       console.error("createDeviceManager errCode:" + err.code + ",errMessage:" + err.message);
       return;
     }
     console.info("createDeviceManager success");
     let dmInstance = data;
   });

  // 使用deviceManager获取目标设备NetworkId
  let deviceList: Array<deviceManager.DeviceInfo> = dmInstance.getTrustedDeviceListSync();
  let networkId: string = deviceList[0].networkId;
  let want: Want = {
    bundleName: "ohos.rpc.test.server",
    abilityName: "ohos.rpc.test.service.ServiceAbility",
    deviceId: networkId,
    flags: 256
  };
  // 建立连接后返回的Id需要保存下来，在断开连接时需要作为参数传入
  // FA模型使用此方法连接服务
  // connectId = featureAbility.connectAbility(want, connect);

  connectId = this.context.connectServiceExtensionAbility(want,connect);
   ```


3. 服务端处理客户端请求

   服务端被绑定的Ability在onConnect方法里返回继承自rpc.RemoteObject的对象，该对象需要实现onRemoteMessageRequest方法，处理客户端的请求。

   ```ts
   onConnect(want: Want) {
       const robj: rpc.RemoteObject = new Stub("rpcTestAbility");
       return robj;
   }
   class Stub extends rpc.RemoteObject {
       constructor(descriptor: string) {
           super(descriptor);
       }
       onRemoteMessageRequest(code: number, data: rpc.MessageSequence, reply: rpc.MessageSequence, option: rpc.MessageOption): boolean | Promise<boolean> {
           // 根据code处理客户端的请求
           return true;
       }
   }
   ```

4. 客户端处理服务端响应

   客户端在onConnect回调里接收到代理对象，调用sendRequest方法发起请求，在期约（JavaScript期约：用于表示一个异步操作的最终完成或失败及其结果值）或者回调函数里接收结果。

   ```ts
   import rpc from '@ohos.rpc';
   // 使用期约
   let option = new rpc.MessageOption();
   let data = rpc.MessageParcel.create();
   let reply = rpc.MessageParcel.create();
   // 往data里写入参数
   proxy.sendRequest(1, data, reply, option)
       .then((result: rpc.SendRequestResult) => {
           if (result.errCode != 0) {
               console.error("send request failed, errCode: " + result.errCode);
               return;
           }
           // 从result.reply里读取结果
       })
       .catch((e: Error) => {
           console.error("send request got exception: " + e);
       })
       .finally(() => {
           data.reclaim();
           reply.reclaim();
       })

   // 使用回调函数
   function sendRequestCallback(result: rpc.SendRequestResult) {
       try {
           if (result.errCode != 0) {
               console.error("send request failed, errCode: " + result.errCode);
               return;
           }
           // 从result.reply里读取结果
       } finally {
           result.data.reclaim();
           result.reply.reclaim();
       }
   }
   let option = new rpc.MessageOption();
   let data = rpc.MessageParcel.create();
   let reply = rpc.MessageParcel.create();
   // 往data里写入参数
   proxy.sendRequest(1, data, reply, option, sendRequestCallback);
   ```

5. 断开连接

   IPC通信结束后，FA模型使用featureAbility的接口断开连接，Stage模型在获取context后用提供的接口断开连接。

   ```ts
   import rpc from "@ohos.rpc";
   // 仅FA模型需要导入@ohos.ability.featureAbility
   // import featureAbility from "@ohos.ability.featureAbility";
   function disconnectCallback() {
       console.info("disconnect ability done");
   }
   // FA模型使用此方法断开连接
   // featureAbility.disconnectAbility(connectId, disconnectCallback);

   this.context.disconnectServiceExtensionAbility(connectId);
   ```

## 相关实例

针对IPC与RPC通信开发，有以下相关实例可供参考：

- [RPC通信（ArkTS）（API9）](https://gitee.com/openharmony/applications_app_samples/tree/master/code/BasicFeature/Connectivity/RPC)