# Overview

In order to be compatible with Web3.js, LoomProvider added some methods that follow the Ethereum JSON RPC API specification. Those methods are callable directly by the Loom QueryService or by LoomProvider. In this tutorial, we're going to talk about LoomProvider.

# LoomProvider calling JSON RPC Methods

The provider should be the bridge between the client and the Loom DAppChain. The code below is an example of LoomProvider been instantiated:

const privateKey = CryptoUtils.generatePrivateKey();
const publicKey = CryptoUtils.publicKeyFromPrivateKey(privateKey);

// Create the client
const client = new Client(
  "default",
  "ws://127.0.0.1:46658/websocket",
  "ws://127.0.0.1:46658/queryws"
);

// The address for the caller of the function
const from = LocalAddress.fromPublicKey(publicKey).toString();

// Instantiate loom provider
const loomProvider = new LoomProvider(client, privateKey);

# eth_accounts

# Description

Returns a list of addresses owned by the LoomProvider

# Parameters

None

# Returns

Array of DATA, 20 Bytes- addresses owned by the client.

# Example

// eth_accounts JSON RPC call
const jsonRPCString = '{"id": 1,"jsonrpc": "2.0", "method": "eth_accounts", "params": []}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

It should return something like this:

{
  "id":1,
  "jsonrpc": "2.0",
  "result": ["0x407d73d8a49eeb85d32cf465507dd71d507100c1"]
}

# eth_blockNumber

# Description

Returns the number of the most recent completed block.

# Parameters

None

# Returns

QUANTITY - integer of the current block number the client is on.

# Example

// eth_blockNumber JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":83}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The function would return something like this:

{
  "id":83,
  "jsonrpc": "2.0",
  "result": "0x4b7" // 1207
}

# eth_call

# Description

Executes a new message call immediately without creating a transaction on the blockchain.

# Parameters

1. Object - The transaction call object

• from: DATA, 20 Bytes - The address the transaction is sent from.
• to: DATA, 20 Bytes - The address the transaction is directed to.
• data: DATA - Hash of the method signature and encoded parameters. For details see Ethereum Contract ABI

# Returns

DATA - the return value of the executed contract.

# Example

// eth_call JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_call","params":[{see above}],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The returned value should look something like:

{
"id":1,
  "jsonrpc": "2.0",
  "result": "0x"
}

# eth_getBlockByNumber

# Description

Returns information about a block by block number.

# Parameters

1. QUANTITY|TAG:

• an integer representing the block number, or -a string which can take one the following values- "earliest", "latest" or "pending", as in the default block parameter.

2. Boolean - If true, it returns the full transaction objects. If false, it returns only the hashes of the transactions.

# Returns

Object - A block object, or null when no block was found:

• number: QUANTITY - the block number. null when it's a pending block.
• hash: DATA, 32 Bytes - hash of the block. null when it's a pending block.
• parentHash: DATA`, 32 Bytes - hash of the parent block.
• logsBloom: DATA, 256 Bytes - the bloom filter for the logs of the block. null when it's a pending block.
• timestamp: QUANTITY - the Unix timestamp for when the block was collated.
• transactions: Array - Array of transaction objects, or 32 Bytes transaction hashes depending on the last given parameter.

# Example

// eth_getBlockByNumber JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x1b4", true],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

This would return something like this:

{
"id":1,
"jsonrpc":"2.0",
"result": {
  "number": "0x1b4", // 436
    "hash": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
    "parentHash": "0x9646252be9520f6e71339a8df9c55e4d7619deeb018d2a3f2d21fc165dde5eb5",
  "logsBloom": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
  "timestamp": "0x54e34e8e" // 1424182926
  "transactions": [{...},{ ... }]
  }
}

# eth_getBlockByHash

# Description

Returns information about a block by hash.

# Parameters

1. DATA - 32 Bytes - Hash of a block.
2. Boolean - If true it returns the full transaction objects if false only the hashes of the transactions.

# Returns

Object - A block object, or null when no block was found:

• number: QUANTITY - the block number. null when it's a pending block.
• hash: DATA, 32 Bytes - hash of the block. null when it's a pending block.
• parentHash: DATA, 32 Bytes - hash of the parent block.
• logsBloom: DATA, 256 Bytes - the bloom filter for the logs of the block. null when it's a pending block.
• timestamp: QUANTITY - the Unix timestamp for when the block was collated.
• transactions: Array - Array of transaction objects, or 32 Bytes transaction hashes depending on the last given parameter.

# Example

// eth_getBlockByHash JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params":["0xb903239f8543d04b5dc1ba6579132b143087c68db1b2168786408fcbce568238"],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The function would return something like this:

{
"id":1,
"jsonrpc":"2.0",
"result": {
    "number": "0x1b4", // 436
    "hash": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
    "parentHash": "0x9646252be9520f6e71339a8df9c55e4d7619deeb018d2a3f2d21fc165dde5eb5",
    "logsBloom": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
    "timestamp": "0x54e34e8e" // 1424182926
    "transactions": [{...},{ ... }]
  }
}

# eth_getCode

# Description

Returns the code at a given address.

# Parameters

1. DATA, 20 Bytes - address

# Returns

DATA - the code from the given address.

# Example

// eth_getCode JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getCode","params":["0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b", "0x2"],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The return value would look similar to this:

{
  "id":1,
  "jsonrpc": "2.0",
  "result": "0x600160008035811a818181146012578301005b601b6001356025565b8060005260206000f25b600060078202905091905056"
}

# eth_getFilterChanges

# Description

Polling method for a filter, which returns an array of logs which occurred since the last poll.

# Parameters

1. QUANTITY - the filter id.

# Returns

Array - Array of log objects, or an empty array if nothing has changed since the last poll.

• For filters created with eth_newBlockFilter, the return values are block hashes (DATA, 32 Bytes), e.g. ["0x3454645634534..."].

• For filters created with eth_newPendingTransactionFilter, the return values are transaction hashes (DATA, 32 Bytes), e.g. ["0x6345343454645..."].

• For filters created with eth_newFilter, logs are objects with following params:

  • removed: TAG - true when the log was removed due to a chain reorganization. false if it's a valid log.
  • logIndex: QUANTITY - integer of the log index position in the block. null when it's a pending log.
  • transactionIndex: QUANTITY - integer index of the transactions index position the log was created from. null when it's a pending log.
  • transactionHash: DATA, 32 Bytes - hash of the transactions this log was created from. null when it's a pending log.
  • blockHash: DATA, 32 Bytes - hash of the block where this log was in. null when it's pending. null when it's a pending log.
  • blockNumber: QUANTITY - the block number where this log was in. null when it's pending. null when it's a pending log.
  • address: DATA, 20 Bytes - address from which this log originated.
  • data: DATA - contains one or more 32 Bytes non-indexed arguments of the log.
  • topics: Array of DATA - Array of 0 to 4 32 Bytes DATA of indexed log arguments. In Solidity, the first topic is the hash of the signature of the event (e.g. Deposit(address,bytes32,uint256), except if you declared the event with the anonymous specifier.

# Example

// eth_getFilterChanges JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getFilterChanges","params":["0x16"],"id":73}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The returned value would look like:

{
  "id":1,
  "jsonrpc":"2.0",
  "result": [{
    "logIndex": "0x1", // 1
    "blockNumber":"0x1b4", // 436
    "blockHash": "0x8216c5785ac562ff41e2dcfdf5785ac562ff41e2dcfdf829c5a142f1fccd7d",
    "transactionHash":  "0xdf829c5a142f1fccd7d8216c5785ac562ff41e2dcfdf5785ac562ff41e2dcf",
    "transactionIndex": "0x0", // 0
    "address": "0x16c5785ac562ff41e2dcfdf829c5a142f1fccd7d",
    "data":"0x0000000000000000000000000000000000000000000000000000000000000000",
    "topics": ["0x59ebeb90bc63057b6515673c3ecf9438e5058bca0f92585014eced636878c9a5"]
    },{
      ...
    }]
}

# eth_getLogs

# Description

Returns an array of all logs matching a given filter object.

# Parameters

1. Object - The filter options:

• fromBlock: QUANTITY|TAG - (optional, default: "latest") Integer block number, or "latest" for the last mined block or "pending", "earliest" for not yet mined transactions.
• toBlock: QUANTITY|TAG - (optional, default: "latest") Integer block number, or "latest" for the last mined block or "pending", "earliest" for not yet mined transactions.
• address: DATA|Array, 20 Bytes - (optional) Contract address or a list of addresses from which logs should originate.
• topics: Array of DATA, - (optional) Array of 32 Bytes DATA topics. Topics are order-dependent. Each topic can also be an array of DATA with "or" options.
• blockhash: DATA, 32 Bytes - (optional, future) With the addition of EIP-234, blockHash will be a new filter option which restricts the logs returned to the single block with the 32-byte hash blockHash. Using blockHash is equivalent to fromBlock = toBlock = the block number with hash blockHash. If blockHash is present in the filter criteria, then neither fromBlock nor toBlock are allowed.

# Returns

See eth_getFilterChanges

# Example

// eth_getFilterChanges JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getLogs","params":[{"topics":["0x000000000000000000000000a94f5374fce5edbc8e2a8697c15331677e6ebf0b"]}],"id":74}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

Result see eth_getFilterChanges

# eth_getTransactionReceipt

# Description

Returns the receipt of a transaction by transaction hash.

The receipt is not available for pending transactions.

# Parameters

1. DATA, 32 Bytes - hash of a transaction

# Returns

Object - A transaction receipt object, or null when no receipt was found:

• transactionHash: DATA, 32 Bytes - hash of the transaction.
• transactionIndex: QUANTITY - integer of the transactions index position in the block.
• blockHash: DATA, 32 Bytes - hash of the block where this transaction was in.
• blockNumber: QUANTITY - block number where this transaction was in.
• from: DATA, 20 Bytes - address of the sender.
• to: DATA, 20 Bytes - address of the receiver. null when it's a contract creation transaction.
• contractAddress: DATA, 20 Bytes - The contract address created, if the transaction was a contract creation. Otherwise, null.
• logs: Array - Array of log objects generated by this transaction.
• status: QUANTITY either 1 (success) or 0 (failure)

# Example

// eth_getTransactionReceipt JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_getTransactionReceipt","params":["0xb903239f8543d04b5dc1ba6579132b143087c68db1b2168786408fcbce568238"],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

It'll return something like this:

{
"id":1,
"jsonrpc":"2.0",
"result": {
    transactionHash: '0xb903239f8543d04b5dc1ba6579132b143087c68db1b2168786408fcbce568238',
    transactionIndex:  '0x1', // 1
    blockNumber: '0xb', // 11
    blockHash: '0xc6ef2fc5426d6ad6fd9e2a26abeab0aa2411b7ab17f30a99d3cb96aed1d1055b',
    contractAddress: '0xb60e8dd61c5d32be8058bb8eb970870f07233155', // or null, if none was created
    logs: [{
        // logs as returned by getFilterLogs, etc.
    }, ...],
    status: '0x1'
  }
}

# eth_newBlockFilter

# Description

Creates a filter, to notify when new pending transactions arrive. To check if the state has changed, call eth_getFilterChanges.

# Parameters

None

# Returns

QUANTITY - A filter id.

# Example

// eth_newBlockFilter JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_newBlockFilter","params":[],"id":73}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

Return value:

"id":1,
{
"jsonrpc":  "2.0",
"result": "0x1" // 1
}

# eth_newFilter

# Description

Creates a filter object, based on filter options, to notify when the state changes (logs). To check if the state has changed, call eth_getFilterChanges.

# A note on specifying topic filters:

Topics are order-dependent. A transaction with a log with topics [A, B] will be matched by the following topic filters:

• [] "anything"
• [A] "A in the first position (and anything after)"
• [null, B] "anything in first position AND B in second position (and anything after)"
• [A, B] "A in the first position AND B in second position (and anything after)"
• [[A, B], [A, B]] "(A OR B) in first position AND (A OR B) in second position (and anything after)"

# Parameters

1. Object - The filter options:

• fromBlock: QUANTITY|TAG - (optional, default: "latest") Integer block number, or "latest" for the last mined block or "pending", "earliest" for not yet mined transactions.
• toBlock: QUANTITY|TAG - (optional, default: "latest") Integer block number, or "latest" for the last mined block or "pending", "earliest" for not yet mined transactions.
• address: DATA|Array, 20 Bytes - (optional) Contract address or a list of addresses from which logs should originate.
• topics: Array of DATA, - (optional) Array of 32 Bytes DATA topics. Topics are order-dependent. Each topic can also be an array of DATA with "or" options.

# Returns

QUANTITY - A filter id

# Example

// eth_newFilter JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_newFilter","params":[{"topics":["0x12341234"]}],"id":73}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The return value should be something like:

{
  "id":1,
  "jsonrpc": "2.0",
  "result": "0x1" // 1
}

# eth_sendTransaction

# Description

Creates a new message call transaction or a contract creation, if the data field contains code.

# Parameters

1. Object - The transaction object

• from: DATA, 20 Bytes - The address the transaction is sent from.
• to: DATA, 20 Bytes - (optional when creating a new contract) The address the transaction is directed to.
• data: DATA - The compiled code of a contract OR the hash of the invoked method signature and encoded parameters. For details see the Ethereum Contract ABI

# Returns

DATA, 32 Bytes - the transaction hash, or the zero hash if the transaction is not yet available.

Use eth_getTransactionReceipt to get the contract address, after the transaction was mined, when you created a contract.

# Example

// eth_sendTransaction JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_sendTransaction","params":[{see above}],"id":1}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

```json
{
  "id":1,
  "jsonrpc": "2.0",
  "result": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331"
}

# eth_subscribe

# Description

It works by subscribing to particular events. The node will return a subscription id. For each event that matches the subscription, a notification with relevant data is send together with the subscription id.

# Parameters

1. object with the following (optional) fields:

• address, either an address or an array of addresses. Only logs that are created from these addresses are returned (optional)
• topics, only logs which match the specified topics (optional)

# Returns

Subscription id

# Example

// eth_subscribe JSON RPC call
const jsonRPCString = '{"id": 1, "method": "eth_subscribe", "params": ["logs", {"address": "0x8320fe7702b96808f7bbc0d4a888ed1468216cfd", "topics": ["0xd78a0cb8bb633d06981248b816e7bd33c2a35a6089241d099fa519e361cab902"]}]}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

The return value should look something like:

{
  "jsonrpc":"2.0",

  "id":2,
  "result":"0x4a8a4c0517381924f9838102c5a4dcb7"
}

# eth_uninstallFilter

# Description

Uninstalls a filter with the given id. It should always be called when watching is no longer needed. Note that filters time out when they aren't requested with eth_getFilterChanges for a period of time.

# Parameters

1. QUANTITY - The filter id

# Returns

Boolean - true if the filter was successfully uninstalled, otherwise false.

# Example

// eth_uninstallFilter JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"eth_uninstallFilter","params":["0xb"],"id":73}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))

It returns something like this:

{
  "id":1,
  "jsonrpc": "2.0",
  "result": true
  }

# net_version

# Description

Returns the current network id.

# Parameters

None

# Returns

String - The current network id.

• "474747": If there's now network id defined, it simply returns 474747.

# Example

// net_version JSON RPC call
const jsonRPCString = '{"jsonrpc":"2.0","method":"net_version","params":[],"id":67}'

// Parse JSON is a necessary step before send
await loomProvider.sendAsync(JSON.parse(jsonRPCString))
``

The return value should look something like:

```json
{
  "id":67,
  "jsonrpc": "2.0",
  "result": "474747"
}