- Add transaction
Add transaction to what?
- Sign the transaction by private key
The code for the RPC command
signrawtransactionwithwallet can be found
here. Follow the code and it will take you to where transactions are actually signed. Starting with this command shows you the whole process.
- Check the transaction by nodes
- Add to mempool
Checking a transaction is done when it is being added to the mempool (the same functions are used for checking transactions in blocks). Just follow the code for
AcceptToMemoryPool