On this page

  2. Antara
  3. Tutorials
  4. Using the Contracts on a Komodo based Blockchain
latest contributor to this doc

Last Edit:

@gcharang↗

Using the Contracts on a Komodo based Blockchain

A high level overview of the Komodo Custom Consensus Framework: How to write UTXO based CryptoConditions contracts for KMD chains - by jl777

To use the contracts on the blockchain, the start command of the chain should contain the parameter -ac-cc .

A brief overview of the -ac-cc parameter:

  • A chain with -ac_cc=N with N 0, will have CC active
  • If N is 1, then it just enables CC
  • if N is >= 2 and <= 100, it allows for non-fungible cross chain contracts within all the chains with the same N value
  • if N >= 101, then it forms a cluster of all the chains with the same N value where the base tokens in all the chains in that cluster are fungible via the burn protocol

To test the contracts

  • Compile Komodo

  • Navigate to src directory, start the test chain with your pubkey and issue the SmartContract RPC commands. All the instructions to get you started are below. For a more elaborate explanation on creating a new blockchain using Komodo see: Creating Komodo Smart Chains

#Install dependencies

cd ~
sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get install build-essential pkg-config libc6-dev m4 g++-multilib autoconf libtool ncurses-dev unzip git python zlib1g-dev wget bsdmainutils automake libboost-all-dev libssl-dev libprotobuf-dev protobuf-compiler libgtest-dev libqt4-dev libqrencode-dev libdb++-dev ntp ntpdate nano software-properties-common curl libcurl4-gnutls-dev cmake clang

Build Komodo

cd ~
git clone https://github.com/jl777/komodo
cd komodo
git checkout jl777
./zcutil/fetch-params.sh
./zcutil/build.sh -j\$(nproc)

Start the Test Chain

cd ~/komodo/src
./komodod -ac_cc=1 -ac_name=<CHAIN_NAME-addressindex=1 -spentindex=1 -ac_supply=1000 -ac_reward=10000000000000 -pubkey=<your_pub_key-addnode=195.201.20.230 -addnode=195.201.137.5 -addnode=195.201.20.230 -addnode=94.130.224.11 &

Relevant info:

(Going through the comments in the following files gives a pretty good overview)

To add a new contract

  1. Add EVAL_CODE to eval.h

  2. Initialize the variables in the CCinit function below

  3. Write a Validate function to reject any unsanctioned usage of vin/vout

  4. Make helper functions to create rawtx for RPC functions

  5. Add rpc calls to rpcserver.cpp and rpcserver.h and in one of the rpc.cpp files

  6. Add the new .cpp files to src/Makefile.am

1, 2 and 6 are not even coding tasks. 4 and 5 are non-consensus time, mostly dealing with JSON. 3 is the main work needed, which makes sense as a different 3 is what makes it a different contract. A lot of a contracts can use slightly modified functions from the other CC contracts. So the best way to do a new one would be to pick the one that is closest to what you want and start morphing it.

General guidance on reporting issues on discord (Regarding CryptoConditions and SmartContract development)

  • the specific chain parameters so anyone can connect to it

  • the EXACT rpc call and parameters you used

  • the most important! : the raw tx generated

  • clear description of why you think it is a bug. for now you need to look at the raw tx details to make sure all vins are valid, signed and all vouts are sane.

  • Please don't post things like "I tried X and it didnt work" as that does not help at all at this stage. These are raw transaction level things and until everything works, things won't work at the higher level.

Discord Invite