How to sign a TX offline by Solana SDK? And then send it afterwards

Question

I need to prepare in advance, for a month, a 100 of TXs signed in offline, for SOL and USDT, USDC.

In the documentation - offline transactions - it's described how to sign them via the cli utilities which isn't what I need to. How would I do this via the Solana SDK/web3?

And how would I then send or broadcast them when I need to? For in the SDK there's a method signAndBroadcast(...), whereas in the case of offline signing, for broadcasting there'll have to be used a separate method, right?

Answer 1

You'll definitely need to use nonce accounts to sign and eventually send these transactions.

If you want to send these all at once, you'll need to create 100 nonce accounts, sign each transaction with the blockhash stored in the nonce account, serialize / store the signed transactions somewhere, and then send them with sendRawTransaction https://github.com/solana-labs/solana-web3.js/blob/fbd397436f622a9b87a7251c08bd9664599299ee/packages/library-legacy/src/connection.ts#L5876

Here's an example from the tests about how to create a transaction with nonceInfo: https://github.com/solana-labs/solana-web3.js/blob/fbd397436f622a9b87a7251c08bd9664599299ee/packages/library-legacy/test/program-tests/system.test.ts#L387-L411