L1-L2 interaction via Postman
Postman is a Starknet utility that allows testing L1-L2 interaction. Ensure you have an L1 node and a Devnet (L2 node) running, load a messaging contract, and flush the queue when needed. You can use starknet-devnet-js to perform these actions, as witnessed in this example, or directly send requests to the endpoints specified below.
Load
POST /postman/load_l1_messaging_contract
{
"networkUrl": "http://localhost:8545",
"address": "0x123...def"
}
JSON-RPC
{
"jsonrpc": "2.0",
"id": "1",
"method": "devnet_postmanLoad",
"params": {
"networkUrl": "http://localhost:8545",
"address": "0x123...def"
}
}
Loads a MockStarknetMessaging contract. The address parameter is optional; if provided, the MockStarknetMessaging contract will be fetched from that address, otherwise a new one will be deployed.
networkUrl is the URL of the JSON-RPC API of the L1 node you've run locally or that already exists; possibilities include, and are not limited to:
Flush
POST /postman/flush
JSON-RPC
{
"jsonrpc": "2.0",
"id": "1",
"method": "devnet_postmanFlush"
}
Goes through the newly enqueued messages, sending them from L1 to L2 and from L2 to L1. Requires no body. Optionally, set the dry_run specifier to just see the result of flushing, without actually triggering it:
POST /postman/flush
{ "dry_run": true }
JSON-RPC
{
"jsonrpc": "2.0",
"id": "1",
"method": "devnet_postmanFlush",
"params": {
"dry_run": true
}
}
A running L1 node is required if dry_run is not set.
Disclaimer
This method of L1-L2 communication testing differs from how Starknet mainnet and testnets work. Taking L1L2Example.sol (originally from Starknet documentation, no longer available there):
constructor(IStarknetCore starknetCore_) public {
starknetCore = starknetCore_;
}
The constructor takes an IStarknetCore contract as argument, however for Devnet's L1-L2 communication testing, this has to be replaced with the logic in MockStarknetMessaging.sol:
constructor(MockStarknetMessaging mockStarknetMessaging_) public {
starknetCore = mockStarknetMessaging_;
}
Mock transactions
L1->L2
Sending mock transactions from L1 to L2 without the need for running L1. Deployed L2 contract address l2_contract_address and entry_point_selector must be valid otherwise new block will not be created.
Normally nonce is calculated by L1 StarknetContract and it's used in L1 and L2. In this case, we need to provide it manually.
A running L1 node is not required for this operation.
POST /postman/send_message_to_l2
Request:
{
"l2_contract_address": "0x00285ddb7e5c777b310d806b9b2a0f7c7ba0a41f12b420219209d97a3b7f25b2",
"entry_point_selector": "0xC73F681176FC7B3F9693986FD7B14581E8D540519E27400E88B8713932BE01",
"l1_contract_address": "0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512",
"payload": [
"0x1",
"0x2"
],
"paid_fee_on_l1": "0x123456abcdef"
"nonce":"0x0"
}
JSON-RPC
{
"jsonrpc": "2.0",
"id": "1",
"method": "devnet_postmanSendMessageToL2",
"params": {
"l2_contract_address": "0x00285ddb7e5c777b310d806b9b2a0f7c7ba0a41f12b420219209d97a3b7f25b2",
"entry_point_selector": "0xC73F681176FC7B3F9693986FD7B14581E8D540519E27400E88B8713932BE01",
"l1_contract_address": "0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512",
"payload": [
"0x1",
"0x2"
],
"paid_fee_on_l1": "0x123456abcdef"
"nonce":"0x0"
}
}
Response:
{ "transaction_hash": "0x0548c761a9fd5512782998b2da6f44c42bf78fb88c3794eea330a91c9abb10bb" }
L2->L1
Sending mock transactions from L2 to L1.
Deployed L2 contract address l2_contract_address and l1_contract_address must be valid.
A running L1 node is required for this operation.
POST /postman/consume_message_from_l2
Request:
{
"l2_contract_address": "0x00285ddb7e5c777b310d806b9b2a0f7c7ba0a41f12b420219209d97a3b7f25b2",
"l1_contract_address": "0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512",
"payload": ["0x0", "0x1", "0x3e8"],
}
JSON-RPC
{
"jsonrpc": "2.0",
"id": "1",
"method": "devnet_postmanConsumeMessageFromL2",
"params": {
"l2_contract_address": "0x00285ddb7e5c777b310d806b9b2a0f7c7ba0a41f12b420219209d97a3b7f25b2",
"l1_contract_address": "0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512",
"payload": ["0x0", "0x1", "0x3e8"],
}
}
Response:
{"message_hash": "0xae14f241131b524ac8d043d9cb4934253ac5c5589afef19f0d761816a9c7e26d"}