I would like to use web3j and to execute the functions of contracts that are found on Binance Smart Chain. How is this done ?

Would it be just

Web3j web3 = Web3j.build(new HttpService("https://bsc-dataseed.binance.org/"))

Then, how do I set the chain ID to 0x38 ?

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    The chain id is needed when u sign a transaction, when you init the transaction manger , there is a param called chainId of type Long
    – Majd TL
    Apr 17, 2021 at 22:43
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    github.com/web3j/web3j/blob/master/core/src/main/java/org/web3j/… there are other types to transaction managers , u can also use raw transaction without manager and give the chain id in the sign method, I can provide an example but in about 12 h
    – Majd TL
    Apr 17, 2021 at 22:49
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    @MajdTL Please provide an example, if not for me, then for others who are looking for answers. Thank you! Apr 17, 2021 at 23:22

1 Answer 1


If you are using the smart contact wrapper then you usually need to give one of the available transaction managers as a parameter and then give the chain Id when you initialize it

Web3j web3 = Web3j.build(new HttpService("https://bsc-dataseed.binance.org/"));
long chainId = 56;
FastRawTransactionManager txMananger = new FastRawTransactionManager(web3, <your-credentials-instance>, chainId);
MyContract contract = new MyContract(<address of contract>, web3, txManager, new DefaultGasProvider());

if you are not using the web3j wrapper and build your transaction manually then:

Web3j web3 = Web3j.build(new HttpService("https://bsc-dataseed.binance.org/"));
long chainId = 56;
RawTransaction rawTransaction = RawTransaction.createTransaction(<address-nonce>, <gas price as big integer>, <gas limit as big integer>, <contract address>, <endcoded function of contract>);
byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, chainId , <you Credentials>);
String hexValue = Numeric.toHexString(signedMessage);
EthSendTransaction transactionResponse = web3 .ethSendRawTransaction(hexValue).sendAsync().get();
  • 1
    Thank you. (some characters to fill in the necessary length to add a comment) Apr 18, 2021 at 22:58

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