Transport

com.calimero.mero.transport. A port of mero-js src/transport/. The transport is chosen once, when the client is built. After that, client.rpc.execute(contextId, method, argsJson) is the same call against a node and through a relay.

val node = createMeroClient(MeroTransportConfig.Node(MeroConfig(baseUrl = nodeUrl)))
val relay = createMeroClient(
    MeroTransportConfig.Relay(
        relay = relayClient,                         // a RelayClient (connectCloud hands one back)
        session = null,                              // suspend () -> String?: a relay Bearer token
        observe = RelayObserveConfig(nodeKey),       // the relay node's key, for events through a session
        proof = ProofCredential(credential, signer = deviceSigner), // request proofs for admin and SSE
    ),
)

`MeroTransportClient`

member	node	relay
`transport`	`"node"`	`"relay"`
`rpc: ExecuteTransport`	`NodeTransport(mero.rpc)`	`RelayTransport` (warrants)
`canSubscribe`	`true`	a node key or a proof was given
`node: Mero`	✓	throws `MeroStateException`
`relay: RelayClient`	throws	✓
`admin: AdminSurface`	the node’s	the relay’s, as the account (session, else proof); throws with neither
`auth`, `cloud`	✓	throws
`events: SseConnection`	`mero.sse`	observer’s (session) or proof-authenticated; throws with neither
`ws: WsClient` (experimental)	`mero.ws`	observer’s; throws for a proof-only client
`ephemeral: TransportEphemeral`	`Node(EphemeralClient)`	`Relay(RelayPresenceClient)`
`close()`	closes streams	closes observer, proof stream, presence

A missing surface throws and names what is missing. Nothing connects to a node you did not choose.

`ExecuteTransport`

interface ExecuteTransport {
    val kind: String                    // RpcExecution.TRANSPORT_NODE / TRANSPORT_RELAY
    val canSubscribe: Boolean
    suspend fun execute(contextId: String, method: String, argsJson: JsonObject = {}): JsonElement
    suspend fun executeWithMetadata(...): ExecuteResult   // (returns, transport, rootHash?)
    suspend fun migrateMyEntries(contextId: String): MigrateMyEntriesSummary
    suspend fun countMyPending(contextId: String): Int
}

executeAs<T>(…) decodes the return. A null output is JsonNull on both transports. rootHash is set only for a relay write. null means “unknown here”, never “nothing changed”.

`RelayObserver`

A node session over the relay, minted lazily by RelayLogin (account_proof) against the pinned node key. accessToken() is single-flight: callers asking at once share one login. It re-mints within 30 s of expiry, and on every call when the token’s exp cannot be read. events / ws are fed by it, and close() closes what was opened. RelayObserver.of(nodeUrl, nodeKey, …) returns null without a key.

For an account’s delegated client, see Delegated accounts.