FAQ for Dart SDK

Check out the frequently asked questions about the PubNub Dart SDK.

Why is a userId required?

The userId uniquely identifies the client (end user, device, or server). Set and persist a stable value for the lifetime of the user or device; without it, the client cannot connect.

Can I publish and subscribe with one client?

Yes. Use a Subscription for real-time updates and publish from the same PubNub instance.

How do I enable Transport Layer Security (TLS)?

Set ssl: true on the NetworkingModule to enable TLS for all communications with PubNub.

Why am I not receiving messages after subscribing?

Messages published before subscribe() are not delivered by default. Subscribe first, then publish. Use history to fetch earlier messages when needed.

How do I filter messages server-side?

Set filterExpression on the keyset. The Stream Controller add-on must be enabled for your keyset.

Which encryption should I use?

Prefer 256‑bit AES‑CBC via CryptoModule. The legacy 128‑bit option is available for backward compatibility.

How do I configure reconnection behavior?

Set retryPolicy on the NetworkingModule (exponential or linear). Non‑subscribe requests do not retry.

How do I use a proxy?

Provide a custom NetworkingModule that routes traffic through your proxy and origin.

Why does encryption use AES-128 when CryptoModule is configured?

If a call supplies a cipherKey argument (for example, in file encrypt/decrypt helpers), that argument overrides the configured CryptoModule for that operation and uses legacy Advanced Encryption Standard (AES) with 128-bit keys. Remove the cipherKey argument to use the CryptoModule configuration (AES‑256‑CBC), or configure a separate CryptoModule instance for partial encryption scenarios.

For details, refer to CryptoModule configuration.