Mobile (Android/iOS/C++) bindings

[jsamol]

I'm looking into embedding Smoldot into a native mobile application. Has anyone done that already and have fully operational native (C++) bindings that could be used in an Android or iOS application?

[tomaka]

It is unclear to me (I couldn't find the answer on the Internet) whether, when embedding Rust within C/C++, it is possible for the Rust code to use the Rust standard library.

If the answer is yes, then the bindings should be relatively simple to write. If the answer is no, then one will need to implement the PlatformRef trait, which is a bit complicated by doable.

[jsamol]

Oh, I see! It does work indeed after I switched to use the Karura specs found in their repo. Just for me to understand and, hopefully, be able to debug such issues better in future, which parts of the logs gave it away? I don't really see a clear message suggesting there might be connectivity issues.

[tomaka]

There isn't any message that will say that you're not connected, but there is the absence of a message that says that you're connected.

The plan to make this more clear is #1343

[jsamol]

Ok, got it. Thanks for your help, it's very appreciated!

[jsamol]

@tomaka I'm coming with an update and more questions to ask 😅

As I mentioned, I did eventually manage to write bindings that I could run on an Android device and the client, in overall, works. However, when I started using it more and more in my code, I noticed that the client's behaviour is not necessarily something I can rely on.

For example, when I try to call an extrinsic quite early after the app's launch and it's the first time the app is running (so no previously persisted state to continue from), the extrinsic usually fails to submit with the BadProof error. The same transaction passes through on the very next run, which leads me to believe the first attempt might be happening before the client is fully synced and uses outdated data to construct the extrinsic. Is it possible? If so, can I mitigate it somehow?

Other than that, I also get a lot of No node available for storage query and Error trying to access the storage required for the runtime call when, well, querying the storage, usually at the beginning of my app's lifecycle. Is it expected? Any advice what I could do about it?

[tomaka]

I have written https://forum.polkadot.network/t/new-json-rpc-api-mega-q-a/3048/17, which might concern your questions