The inter-process communication (IPC) and remote procedure call (RPC) mechanisms are used to implement cross-process communication. The difference between them lies in that IPC uses the Binder driver to implement cross-process communication within a device, whereas RPC uses the DSoftBus driver to implement cross-process communication across devices. The reason why cross-process communication is needed is that each process has its own independent resources and memory space and one process is not allowed to access the resources and memory space of other processes. IPC and RPC usually use the client-server model, where the client (service requester, that is, the process that requests a service) obtains the proxy of the server (service provider, that is, the process that provides the service) and uses the proxy to read and write data to implement data communication across processes. More specifically, the client constructs a proxy object of the server. The proxy object has the same functions as the server. To access a certain API of the server, you only need to access the corresponding API in the proxy object. The proxy object sends the request to the server, and the server processes the received request and returns the processing result to the proxy object through the driver. Then, the proxy object forwards the processing result to the client. The server registers system abilities (SAs) with the system ability manager (SAMgr), which manages the SAs and provides APIs for clients. To communicate with a specific SA, the client must obtain the proxy of the SA from SAMgr. In the following sections, proxy represents the service requester, and stub represents the service provider.
The inter-process communication (IPC) and remote procedure call (RPC) mechanisms are used to implement cross-process communication. The difference between them lies in that IPC uses the Binder driver to implement cross-process communication within a device, whereas RPC uses the DSoftBus driver to implement cross-process communication across devices. The reason why cross-process communication is needed is that each process has its own independent resources and memory space and one process is not allowed to access the resources and memory space of other processes. IPC and RPC usually use the client-server model, where the client (service requester, that is, the process that requests a service) obtains the proxy of the server (service provider, that is, the process that provides the service) and uses the proxy to read and write data to implement data communication across processes. More specifically, the client constructs a proxy object of the server. The proxy object has the same functions as the server. To access a certain API of the server, you only need to access the corresponding API in the proxy object. The proxy object sends the request to the server, and the server processes the received request and returns the processing result to the proxy object through the driver. Then, the proxy object forwards the processing result to the client. The server registers system abilities (SAs) with the system ability manager (SAMgr), which manages the SAs and provides APIs for clients. To communicate with a specific SA, the client must obtain the proxy of the SA from SAMgr. In the following sections, proxy represents the service requester, and stub represents the service provider.
## Constraints
## Constraints
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- Subscription to death notifications of anonymous stub objects (not registered with SAMgr) is prohibited in RPC.
- Subscription to death notifications of anonymous stub objects (not registered with SAMgr) is prohibited in RPC.
- During cross-process communication across processes, a proxy object cannot be passed back to the device that hosts the stub object pointed by the proxy object. That is, the proxy object pointing to the stub object of the remote device cannot be passed across processes twice on the local device.
- During cross-process communication across processes, a proxy object cannot be passed back to the device that hosts the stub object pointed by the proxy object. That is, the proxy object pointing to the stub object of the remote device cannot be passed across processes twice on the local device.
## **Suggestion**
## **Recommendations**
First, compile an API class and define message codes in the API class for both communication parties to identify operations. Unimplemented APIs are allowed in the API class because it must be inherited by both communication parties and its inheritance classes cannot be abstract classes. When inheriting the API class, both communication parties must implement the unimplemented APIs, so as to make sure that the inheritance classes are not abstract classes.
First, compile an API class and define message codes in the API class for both communication parties to identify operations. Unimplemented APIs are allowed in the API class because it must be inherited by both communication parties and its inheritance classes cannot be abstract classes. When inheriting the API class, both communication parties must implement the unimplemented APIs, so as to make sure that the inheritance classes are not abstract classes.
@@ -7,7 +7,7 @@ IPC/RPC allows you to subscribe to the state changes of a remote stub object. Wh
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@@ -7,7 +7,7 @@ IPC/RPC allows you to subscribe to the state changes of a remote stub object. Wh
This subscription mechanism is applicable when the local proxy object needs to detect death of the process hosting the remote stub object or network detach of the device hosting the remote stub object. When the proxy detects death of the remote stub object, the proxy can clear local resources. Currently, IPC supports death notification for anonymous objects, but RPC does not. That is, you can only subscribe to death notifications of services that have been registered with SAMgr.
This subscription mechanism is applicable when the local proxy object needs to detect death of the process hosting the remote stub object or network detach of the device hosting the remote stub object. When the proxy detects death of the remote stub object, the proxy can clear local resources. Currently, IPC supports death notification for anonymous objects, but RPC does not. That is, you can only subscribe to death notifications of services that have been registered with SAMgr.
## **Development Using Native APIs**
## **Using Native APIs**
| API| Return Value Type| Feature Description|
| API| Return Value Type| Feature Description|
| -------- | -------- | -------- |
| -------- | -------- | -------- |
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@@ -84,7 +84,7 @@ bool result = object->AddDeathRecipient(deathRecipient); // Add a recipient for
result=object->RemoveDeathRecipient(deathRecipient);// Remove the recipient for death notifications.
result=object->RemoveDeathRecipient(deathRecipient);// Remove the recipient for death notifications.
