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Cross-chain Ping Pong

Overview​

In this section, we will create a cross-chain ping pong dApp using Router CrossTalk. Using this dApp, you can send any message (ping) from a source chain to a destination chain and receive an acknowledgment (pong) back to the source chain.

Step-by-Step Guide​

Step 1) Prerequisites
Before you begin, ensure you have met the following requirements:
Step 2) Cloning the Ping Pong Contract Locally Written In Anchor
git clone https://github.com/router-protocol/new-crosstalk-sample.git

After cloning the this repo, change your directory:

cd ./solana
Step 3) Program Structure

Events​

  • AckFromDestination: Acknowledgment event emitted after receiving a message from a destination chain.
  • PingFromSource: Event emitted when a ping is received from a source chain.
  • NewPing: Event emitted when a new ping is sent.

Main Functions​

  • 💡initialize: Initializes the PingPongAccount with details like chain-id , gateway-authority, owner, and fee settings.
  • set_dapp_metadata: Sets the fee payer on the router chain. This enables the chain to deduct the fee from the designated fee payer for any cross-chain request (fees are deducted in ROUTE tokens).
    note

    set_dapp_metadata must be called before invoking the i_ping request.

  • i_ping: Sends a ping to another blockchain, specifying the destination chain, contract, and metadata. Internally, it initializes a request_packet account and sets the destination contract and packet.
    note

    Please note, before making a ping call, approve the fee payer request on explorer.

  • i_receive: Receives a ping from another chain and processes it.
  • i_ack: Acknowledges a message and emits relevant events.

Helper Functions (internal module)​

note

ABI encoding/decoding is not ideal on Solana due to larger packet sizes. It's recommended to use custom packet structures instead.

Implementing the default trait is necessary on Solana to acheive cross-chain functionality.

Step 4) Build Ping Pong Program And Deploy It On Devnet

Build program before deploying

anchor build

Deploy it now on devnet

anchor deploy --provider.cluster devnet --program-name ping_pong
note
  • Before deploying, ensure that the program address is updated in both lib.rs and Anchor.toml. After that, rebuild the program and proceed with the deployment.
Step 5) Using the Ping Pong Program

You can interact with the deployed program with written scripts, to interact add PRIVATE_KEY in .env or else script will try to interact with your locally stored wallet ~/.config/solana/id.json

to initialize​

npx ts-node ./scripts/ping-pong.ts --type "initialize" --net solana-devnet --program_id [PROGRAM_ID] --args "[CHAIN_ID],[GATEWAY_PROGRAM]"
  • For an example of a initialization, refer to this transaction.

to set dapp metadata​

npx ts-node ./scripts/ping-pong.ts --type "set_dapp_metadata" --net solana-devnet --program_id [PROGRAM_ID]  --args "[GATEWAY_PROGRAM],[FEE_PAYER]"
  • For an example of a set dapp metadata, refer to this transaction.

to approve fee payer on router chain​

npx ts-node ./scripts/ping-pong.ts --type "approve_fee_payer" --net solana-devnet --program_id [PROGRAM_ID] --args "[PRIVATE_KEY],[RouterEnv]"
  • For an example of a fee payer approval, refer to this transaction.

to ping​

npx ts-node ./scripts/ping-pong.ts --type "ping" --net solana-devnet --program_id [PROGRAM_ID] --args "[GATEWAY_PROGRAM],[DST_CHAIN_ID],[DST_PING_PONG_CONTRACT]"
  • For an example of a ping to avalanche fuji, refer to this transaction.

to get the destination contract address for Solana when calling from another chain​

npx ts-node ./scripts/ping-pong.ts --type "get_dst_contract" --net solana-devnet --program_id [PROGRAM_ID]
  • For an example, dst contract can be as 0x6279fbdaeec3e50d239ed3ddae459e183d4fe773bc33a9076beda840c2f8b62696802f96e43fa2dc6433c4cc504eb5de43836e0ef686493ca3a0eba2958b554dc9288c5f70612bc1f283dfa410a96af07f9201d2a8b1551abe175279d7b7cc986279fbdaeec3e50d239ed3ddae459e183d4fe773bc33a9076beda840c2f8b626
note
  • When pinging from another chain to Solana, the destination contract address must include the ping_pong_program_id, ping_pong_account_id, event_authority, and program_id. Otherwise, the transaction will not be processed.