How to Integrate VIP-191 (III) — Sponsor’s Side
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This is the last part of the tutorial.
It mainly explains the sponsor’s initiative to inspect the transaction and sign his signature on it. We will use the express.js library to build a framework to receive transmission and return the result.
Before that, I have a hefty wallet on test-net to be a sponsor:
Sponsor’s address: 0x126cdb344f476f25b9fb2050513f425a82f71046
Private key: 5df5e7f22a71dfd3d032ff5eb9dfc7dbe9c950e0671745826639a0423cd45d7f
Balance: [LINK] ← Contains >4000 VTHO to be spent.
Sponsor’s Server Code
The above code is quite simple, with some details to pay attention to:
- The server is listening on
localhost:3000. - The
txis re-constructed from the request, it’s a good time inspecting it. - The
sponsoris using his own private key to sign. - The
sponsor_signatureis returned to the user.
Back to the User’s side
Finally, on the user’s side, it can assemble the final compound signature and post the transaction to the VeChain network!
Let’s continue where we left off from the 2nd tutorial:
The process is quite straightforward, concatenate of user’s signature originSignature and the sponsor’s signature sponsorSignature . Then finally call the POST method to send to our VeChain test-net.
An Example Result
As of writing, I have successfully posted several transactions and all show details of VIP-191 fee delegation feature, for example, the transaction with below ID:
Tx: 0xd8b94a68764f6f49eb33bb7a6e895e0f2565c8c8e1731f1258b188561b581e87 [Web Link]
As we can see from the above picture, the 26.64 VTHO is paid not by the user, but by the sponsor. Hence, the fee delegation is complete.
Conclusion
Due to the length of the article, this VIP-191 tutorial doesn’t show the full source code from the user’s side and the sponsor’s side. I have included a workable sample of user.js and sponsor.js on the Github for you to run.
I hope you like this trilogy of tutorials on VIP-191 of VeChain. As always, may the force be with you!
