Unable to establish WebSocket connection with Firebase C++ SDK

[cqx820]

[REQUIRED] Please fill in the following fields:

• Pre-built SDK from the website or open-source from this repo: Open-source from this repo
• Firebase C++ SDK version: 10.7.0
• Main Firebase Components in concern: Auth
• Other Firebase Components in use: Database
• Platform you are using the C++ SDK on: Linux
• Platform you are targeting: Desktop

[REQUIRED] Please describe the question here:

Expected behavior:

I expect to be able to establish a WebSocket connection using the Firebase C++ SDK and receive real-time updates of the database.

Actual behavior:

The WebSocket connection fails to establish using the Firebase C++ SDK, but a simple WebSocket client I wrote could build a secure connection (wss) to a public websocket server on the same device. The Firebase Realtime Database REST API connection works without any issues.

Description:

I am experiencing an issue with the Firebase C++ SDK, where I am unable to establish a WebSocket connection to the Firebase Realtime Database server. Here is the log message:

DEBUG: [conn_1170] websocket error occurred.  Uri: wss://....firebaseio.com/.ws?ns=...&v=5
DEBUG: Error occurred while establishing connection to wss://....firebaseio.com/.ws?ns=...&v=5
DEBUG: [conn_1170] Closing connection. Reason: 4
DEBUG: [pc_0] Got on disconnect due to 4

However, when I tested the connection using a simple WebSocket client I wrote on the same device, it was able to connect successfully. So it might not be a router's firewall setting issue.

I also tested the connection using the Firebase Realtime Database REST API with the same credential by doing

$ curl "https://....firebaseio.com/.../msg.json?auth=$(cat token)"
<response message>

and it worked without any issues. This suggests that the issue is specific to the WebSocket functionality of the Firebase C++ SDK.

I have checked my code for any errors or issues and ensured that I am using the correct credentials and endpoint URLs. I am using the latest version of the Firebase C++ SDK, and have followed the documentation provided by Firebase.

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[AlmostMatt]

HI, thanks for reporting this issue.

To help us reproduce and understand the issue, could you provide sample code for how you are using the C++ SDK to initialize firebase and interact with the database?

[cqx820]

HI, thanks for reporting this issue.

To help us reproduce and understand the issue, could you provide sample code for how you are using the C++ SDK to initialize firebase and interact with the database?

Hi Matt,

Thanks for your reply. In the beginning, I create an App object by doing

m_options.set_api_key(m_api_key.c_str());
m_options.set_project_id(m_project_id.c_str());
m_options.set_database_url(m_database_url.c_str());
m_options.set_app_id(m_app_id.c_str());

m_app = firebase::App::Create(m_options, m_namespace.c_str());

Then I use the initializer to initialize Auth and Database by doing

firebase::ModuleInitializer initializer;
void* initialize_targets[] = {&m_database, &m_auth};

const firebase::ModuleInitializer::InitializerFn initializers[] = {
      [](::firebase::App* app_inner, void* data) {
        void** targets = static_cast<void**>(data);
        ::firebase::InitResult result;
        *static_cast<::firebase::database::Database**>(targets[0]) =
            ::firebase::database::Database::GetInstance(app_inner, &result);
        return result;
      },
      [](::firebase::App* app_inner, void* data) {
        void** targets = static_cast<void**>(data);
        ::firebase::InitResult result;
        *static_cast<::firebase::auth::Auth**>(targets[1]) =
            ::firebase::auth::Auth::GetAuth(app_inner, &result);
        return result;
      },
  };

  initializer.Initialize(
      m_app, initialize_targets, initializers, sizeof(initializers) / sizeof(initializers[0]));

After that, I start to sign in with a custom token by doing

auto sign_in_future = m_auth->SignInWithCustomToken(token);
wait();

Finally, I get database references and add listeners to listen to database change events. We also listen to connection status by subscribing to .info/connected.

I think the codes I provided above were implemented by following the official instructions and I'm sure that the token I used to sign in is valid. I also reviewed the realtime database security rules and no issue was found. I actually have a few devices running the same code but in different networks, most of them are talking to the rtdb without any issues. To rule out the network/firewall issue, I also wrote a simple websocket client using the same version of the uWebSockets library that Firebase SDK uses and it was able to establish a secure connection to a public websocket server, so the router's firewall might not be the root cause.

Right now I'm still not sure if it's a SDK issue or a network issue or even a server issue. Any thoughts or ideas will be very helpful. Thanks!

By the way, do your team have any plan of updating the version of uWebSockets library? It looks really old to me and it might be out of date.

[a-maurice]

Sorry for the late reply. Unfortunately, we haven't had any luck reproducing the problem on our end, so still not clear what the root cause might be.

For the question about the version of uWebSockets, it is a bit complicated, as newer versions basically rewrote the entire library from scratch, so updating it requires changing the underlying code a bit. It is in our backlog to do so though.