# Productizing 'dataConnectionServiceSample.c' **URL:** \ **Category:** Legato Application Framework\ **Created:** [September 4, 2024, 1:21pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783 "2024-09-04T13:21:46Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 4, 2024, 1:21pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/1 "2024-09-04T13:21:46Z")
# Summary I have gotten the wp to connect for short periods of time when there is a good signal and APN values are known. I need to be able to keep connectivity to the WP for years on end, with the exception of a user explicitly turning cell data off or small outages to update APN/Routing settings. I am looking for documentation/code on how to achieve these design goals, specifically the questions below answered. # Questions - WP gets stuck in `connected` state, does not allow disconnect and/or APN updates. How do i fix this? - I am not 100% but this may occur when the program is killed before calling `le_data_Release` - Once in this state not even `cm data` can disconnect the modem or update the APN - If there is a loss of connectivity due to a Cell Network event (IE: Update Location) or loss of signal. Does my program need to detect the loss of the data handler or issue a re-connect or does the legato runtime reconnect for me? - Regarding advanced Cell Routing, do we attach the [example](https://docs.legato.io/latest/c_le_data.html#:~:text=Data%20Connection%20Routing-,Default%20Route,-By%20default%2C%20the) function as a DCS handler like in the example code? Also what are the events that trigger this function? ## References - Code is based primarily on [dataConnectionServiceSample.c](https://docs.legato.io/latest/c_dataConnectionServiceSample.html) - Additional `le_mdc` hooks are added to adjust APN settings - `cm` code is used as a reference, but its use of globals and ConfigTree valaues makes it harder to follow. There is also a [warning](https://docs.legato.io/latest/toolsTarget_cm.html#:~:text=control%20modem%20functions.-,Warning,-This%20tool%20has) saying Customers should not use `cm` in production. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 4, 2024, 1:44pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/2 "2024-09-04T13:44:20Z")
Can you reproduce the problem with cm command only? I suspect your application makes the problem ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 4, 2024, 7:25pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/3 "2024-09-04T19:25:03Z")
@jyijyi you are correct, but that is because `cm` is performing under-documented actions from what i can tell. I think that `cm` avoids the system getting stuck in a connected state by using ` dataConnectionService:/sessionCleanup` in the config tree explicitly. A single header file mentions it use, but it is unclear if the values are just used as a keystore or if it triggers any actions from the runtime. At this point it looks you need to update `dataConnectionSample.c` with mechanisms you use in `cm data` (sessionCleanup and otherwise). I also need the other questions answered from my original post. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 5, 2024, 12:33am UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/4 "2024-09-05T00:33:54Z")
> > > Does my program need to detect the loss of the data handler or issue a re-connect or does the legato runtime reconnect for me? You can see here: > **[le\_data Interface - Legato Docs](https://docs.legato.io/latest/c_le_data.html)** > > legato™ is an open source Linux-based embedded platform designed to simplify connected IoT application development Once an application makes a data connection request, it should monitor the connection state reported to the registered connection state handler. The application should only try transmitting data when the state is connected, and should stop transmitting data when the state is not connected. If the state is not connected, the data connection service will try to establish or re-establish the connection endlessly until [le\_data\_Release()](https://docs.legato.io/latest/group __le__ data.html#ga1dc7cd8faed6b1ee02ea947cf02b8ee7) is called. There’s no need for an application to issue a new connection request. ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 5, 2024, 1:07pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/5 "2024-09-05T13:07:40Z")
Thank you, let me update my original question list # Questions 1. What needs to be added to `dataConnectionSample.c` to make it production ready? - `dataConnectionService:/sessionCleanup` needs to be explained/documented (it looks like this stems from le\_dcs no longer using the Config Tree?) - Regarding Channel Monitoring, `cm` stored `handlerRef` into the config tree in reference to the dcs event handler. Does this handler persists after `cm` is done executing (IE: when the prompt returns after `data connect`)? If not why is it stored in the Config Tree? - Can the `le_data_RequestObjRef_t ` value be stored in the Config tree the same way `le_dcs_RequestObjRef_t` is? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 5, 2024, 3:49pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/6 "2024-09-05T15:49:48Z")
I never use your sample app, but do you see problem with modemdemo to establish data connection? > **[legato-af/apps/sample/modemDemo at master · legatoproject/legato-af](https://github.com/legatoproject/legato-af/tree/master/apps/sample/modemDemo)** > > Legato Application Framework. Contribute to legatoproject/legato-af development by creating an account on GitHub. ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 5, 2024, 4:33pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/7 "2024-09-05T16:33:12Z")
> [@jyijyi](#): > > I never use your sample app My app is essentially your/Legato’s [sample app](https://docs.legato.io/latest/c_dataConnectionServiceSample.html). It is not exactly the same as `modemDemo` as that also performs SMS actions. Both do not perform the `dataConnectionService:/sessionCleanup` step `cm` does so I imagine i am going to get the same `stuck in connected` result. Please answer the questions in the prior comment ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 5, 2024, 4:51pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/8 "2024-09-05T16:51:24Z")
i can see both the `dataConnectionSample.c` and modemdemo are using le\_data\_request() to establish data connection. What is the problem with this API? Have you tried with modemdemo and see if there is problem? ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 5, 2024, 7:41pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/9 "2024-09-05T19:41:02Z")
> [@jyijyi](#): > > What is the problem with this API? > [@upsampled](#): > > WP gets stuck in `connected` state, does not allow disconnect and/or APN updates. How do i fix this? > [@upsampled](#): > > [`cm` avoids this issue because] `cm` is performing under-documented actions from what i can tell. I think that `cm` avoids the system getting stuck in a connected state by using ` dataConnectionService:/sessionCleanup` in the config tree explicitly. It looks like the request reference value, whether from `le_data` or `le_dcs`, is needed to stop a connected state. This is why `cm` stores it in the Config Tree immediately after getting it as `reqRef`, as apps can crash for any reason so the only way to keep that value safe is to put it in outside program memory. As for the other stored value, `handlerRef`, it looks like a similar situation just involving the event monitoring handler (IE: a unique ID is needed to remove the old/unused handler). This information is not included in `modemDemo.c` or `dataConnectionSample.c`. It is just me just trying to figure out why the `cm` tool does not get the system into these states. I need the Legato team to more explicitly confirm/detail/correct my theory about these stored values. > [@jyijyi](#): > > Have you tried with modemdemo and see if there is problem? I have compiled and run `modemDemo` but best I can tell the only way to interact with it is to send the device SMS commands. My sims do not allow SMS commands so this is a non-starter. Best I can tell, if the program was stopped mid IPv4/IPv6 test the WP would get stuck in the connect state just like `dataConnectionSample.c`. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 6, 2024, 1:07am UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/10 "2024-09-06T01:07:49Z")
you can use the following command to run the modemdemo: ```auto app runProc modemDemo1 send --exe=send -- 1234567 "Online" app runProc modemDemo1 send --exe=send -- 1234567 "Offline" ``` All result is in /legato/systems/current/appsWriteable/modemDemo1/smsChat.txt I still don’t quite understand your question, what is the relationship or problem with the config tree and the connected state of the application? Can you list out the full procedure to reproduce your issue with modemdemo application? BTW, do you contact distributor to report this issue if you need official support from legato team? ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 6, 2024, 12:34pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/11 "2024-09-06T12:34:26Z")
> [@jyijyi](#): > > I still don’t quite understand your question, what is the relationship or problem with the config tree and the connected state of the application? My original issue was that the WP77xx was getting stuck in a ‘connected’ state (I could not disconnect or update the APN). My application was based on `dataConnectionSample.c`. I noticed that `cm` did not get into this state so I decided to compare it, mainly `cm_data.c`, to `dataConnectionSample.c`. Besides `cm` using `le_dcs` instead of `le_data`, the primary difference in `cm_data.c` was the use of the `*SessionCleanup*` functions located in it and `dcs_util.c` . These functions are tied directly to Config Tree values and great effort is spent configuring them prior to and after `cm connect`. I am asking for the design reasoning and documentation for functions that interact with ` dataConnectionService:/sessionCleanup/` because of this. > Regarding `modemDemo` The provided commands work, I will continue to see if it also gets stuck in the connected state; however, I am still requesting the `sessionCleanup` documentation. > BTW, do you contact distributor to report this issue if you need official support from legato team? They pointed here. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 6, 2024, 2:26pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/12 "2024-09-06T14:26:58Z")
I think you can first see if modemdemo has problem. If no, then you can port your code to modemdemo app Btw, did you check logread to see why your app cannot change apn? ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 6, 2024, 6:40pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/13 "2024-09-06T18:40:38Z")
Ok, I believe I have determined the issue/behavior that led to the creation of the ticket: 1. Many application can call `le_data_Request` concurrently and they will all receive a valid request objects. 2. As long as 1 of those applications are running and have not release the Request, the connection will be considered ‘in-use’ The confusing part is how `cm`, the primary cell test utility, changes the behavior of the system. 1. If `cm` started the cell connection, and a request to disconnect is issued, then ‘cm’ will report a successful disconnect 2. If there is a `le_data_Request` app running (started after `cm data connect` but before `cm data disconnect`), the lte connection will actually stay connected, making `cm` successful disconnect message confusing. 3. `cm` will get connect and disconnect errors while the `le_data` applications are running going forward. I am still unclear about `le_dcs_Start` requests differ in behavior compared to `le_data_Request` as well as how `sessionCleanup:` modifies the behavior even more (does it allow the connection to stay up after the app terminates or the config tree values are deleted?). Please clear this up and I’ll close the ticket. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 7, 2024, 12:23am UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/14 "2024-09-07T00:23:57Z")
Not quite sure how session cleanup is related to modifying apn or disconnecting data channel … Have you tried to port the session cleanup code to modemdemo and see if it fixes anything if you think this is related? Another test you can do is to test in wp77 firmware r14.1 instead of r15.1, i saw that the session cleanup code is added only in legato 21.5 which is in firmware r15.1. Legato 19.11.5 in firmware r14.1 does not contain such cleanup code. If there is no problem for cm tool in r14.1, that means the session cleanup code is not related to your problem: > Btw, did you check logread to see why your app cannot change apn? Lastly, do you mean that modemdemo is working fine for you now? ---
**Author:** ![upsampled](https://avatars.discourse-cdn.com/v4/letter/u/bc8723/32.png) [@upsampled](https://forum.legato.io/u/upsampled)\ **Post date:** [September 9, 2024, 12:10pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/15 "2024-09-09T12:10:38Z")
> [@jyijyi](#): > > Not quite sure how session cleanup is related to modifying apn or disconnecting data channel I don’t either because it is undocumented. Please feel free to get us on the same page by fixing this. > [@jyijyi](#): > > Have you tried to port the session cleanup code to modemdemo and see if it fixes anything if you think this is related? I have not because session cleanup looks to be coupled with the `le_dcs` api with modemDemo does not use, just `cm`. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [September 9, 2024, 12:31pm UTC](https://forum.legato.io/t/productizing-dataconnectionservicesample-c/6783/16 "2024-09-09T12:31:05Z")
le\_data\_request() is also calling to dcs: > Another test you can do is to test in wp77 firmware r14.1 instead of r15.1, i saw that the session cleanup code is added only in legato 21.5 which is in firmware r15.1. Legato 19.11.5 in firmware r14.1 does not contain such cleanup code. If there is no problem for cm tool in r14.1, that means the session cleanup code is not related to your problem: > Btw, did you check logread to see why your app cannot change apn? Lastly, do you mean that modemdemo is working fine for you now?