prepareSendingNativeSOL fails with APIClientError error 0 on Devnet using latest SolanaSwift v5

[rafaelreverberi]

Hi team,

I’m encountering a persistent issue when using prepareSendingNativeSOL from SolanaSwift 5.0.0.

Everything works until the prepareSendingNativeSOL step, where I get this error:

❌ Fehler bei prepareTransaction: responseError(SolanaSwift.ResponseError(code: Optional(-32601), message: Optional("Method not found"), data: nil))

This happens even though:

• Devnet endpoint is healthy (getHealth returns ok)
• getBalance works
• KeyPair is valid and works
• The transaction amount is low and fee is estimated correctly
• The wallet has more than enough lamports

Here is my relevant code for sendSOL:

let endpoint = APIEndPoint(address: "https://api.devnet.solana.com", network: .devnet)
let apiClient = JSONRPCAPIClient(endpoint: endpoint)
let blockchainClient = BlockchainClient(apiClient: apiClient)

let prepared = try await blockchainClient.prepareSendingNativeSOL(
from: account,
to: address,
amount: lamports
)

The error returned is:
The operation couldn’t be completed. (SolanaSwift.APIClientError error 0.)

I have checked the endpoint health and version:
curl https://api.devnet.solana.com
-X POST -H "Content-Type: application/json"
-d '{"jsonrpc":"2.0","id":1,"method":"getHealth","params":[]}'
→ { "result": "ok" }

curl https://api.devnet.solana.com
-X POST -H "Content-Type: application/json"
-d '{"jsonrpc":"2.0","id":1,"method":"getVersion","params":[]}'
→ solana-core: 2.3.5

What’s the correct RPC method called by prepareSendingNativeSOL under the hood, and is it deprecated or missing on this node?

Any guidance or fixes would be appreciated. Let me know if you need a repro project.

Thanks in advance!
Rafael Reverberi

MyCode.txt

We also facing the same issue

[rafaelreverberi]

We also facing the same issue

Hey! I finally fixed this issue after running into the same problem with prepareSendingNativeSOL.
The root cause is that it uses the deprecated getFees RPC method under the hood, which many nodes (like devnet) no longer support — that's why you get "method not found" or weird deserialization errors.

✅ My solution:
I completely rewrote the flow by manually building and signing the transaction, then calling getFeeForMessage using just the compiled message (not the whole transaction). This gives full control and works on modern RPCs.

Here’s the working part from my function (feel free to use it):

func sendSOL(to address: String, amount: Double) async throws -> String {
// 1) Aktives Wallet prüfen
guard let account = self.account else {
throw WalletManagerError.transactionFailed("Kein aktives Wallet geladen")
}
print("👛 Aktives Wallet: (account.publicKey.base58EncodedString)")
print("📬 Zieladresse: (address)")
print("💸 Betrag in SOL: (amount)")

// 2) JSON‑RPC‑Client initialisieren
let endpoint  = APIEndPoint(address: "https://api.devnet.solana.com", network: .devnet)
let apiClient = JSONRPCAPIClient(endpoint: endpoint)

// 3) Kontostand abfragen
print("📡 Versuche Kontostand abzurufen …")
let balanceLamports: UInt64
do {
    balanceLamports = try await apiClient.getBalance(account: account.publicKey.base58EncodedString)
    print("✅ Kontostand: \(balanceLamports) Lamports")
} catch {
    throw WalletManagerError.network
}

// 4) Betrag umrechnen und einfache Prüfung (ohne Gebühr)
let lamports = UInt64(amount * 1_000_000_000)
print("🔁 Betrag in Lamports: \(lamports)")
guard balanceLamports >= lamports else {
    print("❌ Nicht genügend Guthaben")
    throw WalletManagerError.insufficientBalance
}

// 5) Aktuellen Blockhash abholen
print("🔄 Hole aktuellen Blockhash …")
let blockhash = try await apiClient.getLatestBlockhash()
print("✅ Aktueller Blockhash: \(blockhash)")

// 6) Transfer‑Instruction erzeugen
let instruction = try SystemProgram.transferInstruction(
    from: account.publicKey,
    to: PublicKey(string: address),
    lamports: lamports
)

// 7) Transaction bilden und signieren
var transaction = Transaction(
    instructions: [instruction],
    recentBlockhash: blockhash,
    feePayer: account.publicKey
)
try transaction.sign(signers: [account])
print("✅ Transaktion signiert")

// 8) Gebühr über getFeeForMessage ermitteln (Nachricht kompilieren + serialisieren)
let feeLamports: UInt64
do {
    // 8.1) Nachricht kompilieren (ohne Signaturen)
    let message = try transaction.compileMessage()
    
    // 8.2) Kompilierte Nachricht serialisieren
    let messageData = try message.serialize()
    let messageBase64 = messageData.base64EncodedString()
    print("📦 Base64 Message (für Fee-Request): \(messageBase64)")
    
    // 8.3) RPC‑Call: getFeeForMessage
    feeLamports = try await apiClient.getFeeForMessage(message: messageBase64)
    print("✅ Erforderliche Gebühr: \(feeLamports) Lamports")
    
} catch {
    print("❌ Fehler beim Nachricht-Serialisieren oder Fee-Request: \(error)")
    throw WalletManagerError.transactionFailed("Nachricht/Feerequest fehlgeschlagen: \(error.localizedDescription)")
}


// 9) Finaler Guthaben‑Check inkl. Gebühr
guard balanceLamports >= lamports + feeLamports else {
    print("❌ Nicht genügend Guthaben (inkl. Gebühr)")
    throw WalletManagerError.insufficientBalance
}

// 10) Raw Transaction serialisieren
let rawTxData = try transaction.serialize()
let base64Tx   = rawTxData.base64EncodedString()
print("🔄 RAW TX (base64): \(base64Tx)")

// 11) Sende Transaktion
struct SendTxConfig: Encodable {
    let skipPreflight: Bool
    let encoding:      String
}
let config = SendTxConfig(skipPreflight: true, encoding: "base64")

print("🚀 Sende Transaktion (skipPreflight) …")
let signature: String = try await apiClient.request(
    method: "sendTransaction",
    params: [base64Tx, config]
)
print("✅ Transaktion gesendet! Signature: \(signature)")
return signature

}
Let me know if you want the full function — happy to share!

[rafaelreverberi]

We also facing the same issue

And don’t forget: you need to import the required package in Swift like this:

[rafaelreverberi]

We also facing the same issue

🔗 And if you're curious — here’s the official list of all available Solana RPC methods:
https://solana.com/de/docs/rpc/http