I have written a HTML interface which uses web3.js library. For my testing, I dropped web3.js library into the CoinCode directory and import it in HTML file.

<script type="text/javascript" src="bignumber.js/bignumber.min.js"></script>
<script type="text/javascript" src="web3//dist/web3-light.js"></script>
    var Web3 = require('web3');
    var web3 = new Web3();
    web3.setProvider(new web3.providers.HttpProvider("http://localhost:8019"));

Then, I connected to my contract there by using:

var contract1=web3.eth.contract(abiDefination).at(address);

and I was able to use all the functions of my contract by:


But, how can I make rpc calls to my functions. Like I can use following call to list accounts:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_accounts","params":[],"id":6‌​5}' http://localhost:8019/

Can I use functions of my contract in similar fashion, like:

curl -X POST --data '{"jsonrpc":"2.0","method":"contract1_checkBalance","params":["0x.."],"id":6‌​5}' http://localhost:8019/

and get desired output. Currently when I use such post calls I get:

    "jsonrpc": "2.0"
    "id": 67
    "error": {
        "code": -32601
        "message": "The method contract1_checkBalance does not exist/is not available"

1 Answer 1


Web3 will take care of the RPC calls, so to make a call without a transaction, for instance for checkBalance(), you call it thus:

// If `checkBalance` is `constant`:
var balance = contract1.checkBalance("0x..");
// otherwise
var balance = contract1.checkBalance.call("0x..");

To make a call with a transaction:

var txHash = contract1.transfer(param1, param2, { from: senderAccount });
// or
var txHash = contract1.transfer.sendTransaction(param1, param2, { from: senderAccount });


On the other hand, if you want to make a straight URL call, you need to prepare the data to send with:

var callData = contract1.checkBalance.getData("0x..");

Then your curl call looks like:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_call","params":[{"to": contractAddress, "data": callData}],"id":6‌​5}' http://localhost:8019/

And if you want to send a transaction to your contract, similarly:

var callData = contract1.transfer.getData(param1, param2);

Then you curl call looks like:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_sendTransaction","params":[{"from": account, "to": contractAddress, "data": callData}],"id":6‌​5}' http://localhost:8019/

After you have looked at how data is packaged in this callData, you should be able to assemble it without even the help of contract1.

  • Probably you got me wrong,or I was unclear with my question. I am able to call all my functions like transfer(..), as you are saying, in a JS code. But, i want to know how can I access my functions on localhost:8019/. Currently, I have written code for a HTML page which I rum by double-clicking it. I want to access it on a url like localhost:8019. How can I do that? I have given scenarios like I am able to access eth_accounts method there, but is there anyway I can post a request on localhost:8019 with function name like contract1.checkBalance instead of eth_accounts. Commented Sep 15, 2016 at 12:37
  • I updated the answer with further examples. Commented Sep 15, 2016 at 13:23
  • sorry but I did't get desired output, when I used, curl -X POST --data '{"jsonrpc":"2.0","method":"eth_sendTransaction","params":[{from: "0x1c2DDB63F2084B70a27Ec7da01126dadbE084945", to: "0xcEEFFdd02D22b315ACa57D0180F99C0e5BDA5255", data: contract1.transfer.getData("0x936335307DEfa5a611a00eb0775F176469d5D288", 1100)}],"id":65}' http://localhost:8019 I got {"jsonrpc":"2.0","error":{"code":-32600,"message":"invalid character 'f' looking for beginning of object key string"}} as response. Commented Sep 16, 2016 at 4:29
  • Sorry: must be {"from":... Commented Sep 16, 2016 at 11:16
  • 1
    Note that you may have to add a block parameter to eth_call - see ethereum.stackexchange.com/a/9349/1268. Commented Oct 17, 2016 at 16:04

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