Low Level Messaging API binding woes

[chrisc]

Hi All,

I’m using legato framework 20.04, and I’m trying to use the low level messaging API to communicate between 2 different processes in the same app. I’ve followed the instructions in the following posts:

Low Level Messaging API

It would be helpful if you attached the program which is giving you the error. Are you trying to communicate with a client or server that uses API files? Or are both ends using the low-level messaging API directly?

Low Level message API Opening Session Fails

Hi epsragh, I’ll try to help you on your issue but first I wonder why you want to use the low level message APIs. Usually, these APIs are internal use in Legato and server/clients development in rather done in a bit higher level. Have a look at daemon developments in Legato code to get a better idea (example: le_cellnet.api, le_spi.api). Hope this helps, Regards,

However, I am still unable to connect the client to the server side. This is the pertinent info from my adef file:

    components:
    {
        UEventManager
        UsbManager
    }
    executables:
    {
        UEventManagerExe = ( UEventManager )
        UsbManagerExe = ( UsbManager )
    }
    bindings:
    {
        *.UEvtMgrSvc -> *.UEvtMgrSvc
    }
    sandboxed: false

My UEventManager component has a class with this initialization:

   void _initialize()
    {
        le_msg_ProtocolRef_t protocolRef = le_msg_GetProtocolRef(UEVENT_PROTO_ID, sizeof(struct UEVENT_T));
        mServiceRef                      = le_msg_CreateService(protocolRef, UEVENT_MANAGER_SERVICE);
        le_msg_AddServiceOpenHandler(mServiceRef, &pUEventManagerServer::_new_client_session, this);
        le_msg_AddServiceCloseHandler(mServiceRef, &pUEventManagerServer::_close_client_session, this);
        Debug::Log(Debug::LogLevel::DEBUG_INFO, "Advertising service %p (%s)", mServiceRef, UEVENT_MANAGER_SERVICE);
        le_msg_AdvertiseService(mServiceRef);
    }

My UsbManager has a class with the following method:

    void _initialize()
    {
        le_msg_ProtocolRef_t protocolRef = le_msg_GetProtocolRef(UEVENT_PROTO_ID, sizeof(UEVENT_T));
        mSessionRef                      = le_msg_CreateSession(protocolRef, UEVENT_MANAGER_SERVICE);
        le_msg_SetSessionRecvHandler(mSessionRef, &pUEventManagerClient::_incoming_message_handler, this);
        le_msg_OpenSessionSync(mSessionRef);
        Debug::Log(Debug::LogLevel::DEBUG_INFO, "Opened UEventManagerClient session.");
    }

When I execute my code I get the following in sdir:

    BINDINGS

            <root>.sdirTool -> <root>.sdirTool
            ...
            <root>.UEvtMgrSvc -> <root>.UEvtMgrSvc
            ...

    SERVICES
            ...

    WAITING CLIENTS

            [pid  4201] <root>.UEvtMgrSvc WAITING for <root>.UEvtMgrSvc  (protocol ID = 'UEVENT_MESSAGEv1.0')

Where the bindings are showing up, but the services are not there, and the client is still waiting on the server. However, in logread I get the following lines:

Jan 5 23:42:07 swi-mdm9x28-wp user.info Legato: INFO | UEventManagerExe[7202]/UEventManager T=UEvent Messaging Servic | debug.cpp Log() 37 | UEventManager: Advertising service 0x7f56f870 (UEvtMgrSvc)

So it seems that though I am calling le_msg_AdvertiseService, and even though the bindings are there, and the client is waiting to connect, the service never appears. What am I missing?

Thanks,
Chris

[jyijyi]

I have never used message API, but will you consider to use Ipc communication between components or applications?

Cannot get callback between components (IPC) to work properly

Hi, I’m currently working on an application that must send data from one component (component A) to the other (component B) (via IPC). The sending part is implemented via API in component B. communication.api FUNCTION send ( char buffer[BUFFER_SIZE] IN ); However component B can have data ready at any time for component A. For this case I want to use a callback to send data from component B to component A. I tried the following: communication.api DEFINE BUFFER_SIZE = 64; HANDLER o…

[chrisc]

I’ve taken your suggestion, and I’ve been able to use IPC communications as you’ve outlined in the issue you’ve linked to. It seems to be working, but I will need to dig a little deeper to determine why some handlers seem to go missing.