xdapp-book/projects/evm-messenger/README.md

# EVM Messenger
Simple messenger project that sends a "Hello World" message between two EVM chains using Wormhole. 

## Dependencies
This project uses Foundry to compile and deploy EVM contracts. You can find install instructions at [`https://getfoundry.sh`](http://getfoundry.sh)

The javascript dependencies can be installed via `npm install` in this folder.

## Test Scripts
After you have Guardiand running (you can use the [wormhole-local-validator](https://github.com/wormhole-foundation/xdapp-book/tree/main/projects/wormhole-local-validator), you can run the basic test with `npm run test`. This will: 
- Deploy a simple Messenger contract (found in chains/evm/src/Messenger.sol) to each EVM chain
- Register each contract with the other chain
- Send a message from each contract
- Fetch the VAA from the Guardian
- Submit the VAA to each contract
- Print out the Message

If everything goes correctly, you should get a printout with the Hello World messages on each chain.

## Common Errors
### Nonce Issues
If you see transactions failing due to nonce mismatch errors, restart your local evm chain. If using the [wormhole-local-validator](https://github.com/wormhole-foundation/xdapp-book/tree/main/projects/wormhole-local-validator), just rerun `npm run evm` and then retry `npm run test`.

This is intermittent and likely caused by the js lib and evm chain being out of sync.

### Transaction Underpriced Issues
Transactions failing with the message `transaction underpriced` is an intermittent issue. Restart the evm chains and rerun `npm run test`. If the issue persists, you may need to manually set gas prices when calling the Messenger contract in the `send_msg` logic in `orchestrator.js`.