Add support for creating a NimBLEClient from a NimBLEServer peer.

[h2zero]

This allows the NimBLEServer instance to create a NimBLEClient instance to read/write form/to a connected peer. Only one instance is supported subsequent calls will overwrite the previous client connection information and data.

[h2zero]

@finger563 You may be interested in reviewing this, your feedback would be greatly appreciated.

[finger563]

@finger563 You may be interested in reviewing this, your feedback would be greatly appreciated.

@h2zero It looks like a net improvement to the API for sure, and I like not having to manage the client pointer myself just to talk to the connected client.

One question I do have though is that In my code previously I would unset the client connection (calling clearConnection()) after using it, so that the client could be properly deleted / deinitialized (e.g. when calling NimBLEDevice::deinit(clear_all=true)). I remember getting a hang or crash of some kind if I didn't call the clear connection on the client before calling that, is that something that would still need to be done or would this automatically take care of it now?

[h2zero]

That shouldn't be necessary now because the client is created and managed by the server and NimBLEDevice::deint(true) will only manage the clients created through that interface. The server will delete the client instance when it is deleted so there should be no issues.

[h2zero]

@finger563 Did you perhaps test this at all?

[finger563]

@h2zero Unfortunately, I've not had time to yet. If you need, I'll be able to test late today or tomorrow.

[finger563]

@h2zero one change in behavior I'm seeing when using the new client instead of the one I was using before is that the initial connection (before auth is complete) now returns failure to get generic access service from the client:

Disconnect and reconnect and it works fine.

So that's something that ideally could be fixed?

Code I'm using:

    // since this connection is handled by the server, we won't manually
    // connect, and instead inform the client that we are already connected
    // using this conn handle
    auto client = server_->getClient(conn_info);
    // refresh the services
    client->getServices(true);
    // now get Generic Access Service
    auto gas = client->getService(NimBLEUUID("1800"));
    if (!gas) {
      logger_.error("Failed to get Generic Access Service");
      return {};
    }

[h2zero]

Thanks, not sure why that errored, would need to see logging with info messages on.

[finger563]

@h2zero

Here are some additional (debug) logs turned on esp-nimble-cpp:

[h2zero]

Thanks, found the issue.

@finger563 Just pushed the fix if you could please confirm when you have time?

[finger563]

@h2zero Thanks, confirmed it's fixed :)

[finger563]

Works well in my testing :)

[h2zero]

Great, thanks! I'm considering removing the server name read to go along with this as it seems redundant and bloats the code.