3.0.0-beta • Public • Published


    A modern Syscoin Core REST and RPC client to execute administrative tasks, wallet operations and queries about network and the blockchain.


    npm version build status


    Install the package via npm:

    npm install syscoin-core --save




    1. [agentOptions] (Object): Optional agent options to configure SSL/TLS.
    2. [headers=false] (boolean): Whether to return the response headers.
    3. [host=localhost] (string): The host to connect to.
    4. [logger=debugnyan('syscoin-core')] (Function): Custom logger (by default, debugnyan).
    5. [network=mainnet] (string): The network
    6. [password] (string): The RPC server user password.
    7. [port=[network]] (string): The RPC server port.
    8. [ssl] (boolean|Object): Whether to use SSL/TLS with strict checking (boolean) or an expanded config (Object).
    9. [ssl.enabled] (boolean): Whether to use SSL/TLS.
    10. [ssl.strict] (boolean): Whether to do strict SSL/TLS checking (certificate must match host).
    11. [timeout=30000] (number): How long until the request times out (ms).
    12. [username] (number): The RPC server user name.
    13. [version] (string): Which version to check methods for (read more).


    Using network mode

    The network will automatically determine the port to connect to, just like the syscoind and syscoin-cli commands.

    const Client = require('syscoin-core');
    const client = new Client({ network: 'regtest' });
    Setting a custom port
    const client = new Client({ port: 28332 });

    Connecting to an SSL/TLS server with strict checking enabled

    By default, when ssl is enabled, strict checking is implicitly enabled.

    const fs = require('fs');
    const client = new Client({
      agentOptions: {
        ca: fs.readFileSync('/etc/ssl/syscoind/cert.pem')
      ssl: true

    Connecting to an SSL/TLS server without strict checking enabled

    const client = new Client({
      ssl: {
        enabled: true,
        strict: false

    Using promises to process the response

    client.getInfo().then((help) => console.log(help));

    Using callbacks to process the response

    client.getInfo((error, help) => console.log(help));

    Returning headers in the response

    For compatibility with other Syscoin Core clients.

    const client = new Client({ headers: true });
    // Promise style with headers enabled:
    client.getInfo().then(([body, headers]) => console.log(body, headers));
    // Await style based on promises with headers enabled:
    const [body, headers] = await client.getInfo();

    Floating point number precision in JavaScript

    Due to Javascript's limited floating point precision, all big numbers (numbers with more than 15 significant digits) are returned as strings to prevent precision loss.

    Version Checking

    By default, all methods are exposed on the client independently of the version it is connecting to. This is the most flexible option as defining methods for unavailable RPC calls does not cause any harm and the library is capable of handling a Method not found response error correctly.

    const client = new Client();
    // => RpcError: -32601 Method not found

    However, if you prefer to be on the safe side, you can enable strict version checking. This will validate all method calls before executing the actual RPC request:

    const client = new Client({ version: '0.12.0' });
    // => Method "gethashespersec" is not supported by version "0.12.0"

    If you want to enable strict version checking for the bleeding edge version, you may set a very high version number to exclude recently deprecated calls:

    const client = new Client({ version: `${Number.MAX_SAFE_INTEGER}.0.0` });
    // => Throws 'Method "getwork" is not supported by version "9007199254740991.0.0"'.

    To avoid potential issues with prototype references, all methods are still enumerable on the library client prototype.


    Start the syscoind with the RPC server enabled and optionally configure a username and password:

    docker run --rm -it seegno/syscoind:0.12-alpine -printtoconsole -rpcuser=foo -rpcpassword=bar -server

    These configuration values may also be set on the syscoin.conf file of your platform installation.

    By default, port 8332 is used to listen for requests in mainnet mode, or 18332 in testnet or regtest modes. Use the network property to initialize the client on the desired mode and automatically set the respective default port. You can optionally set a custom port of your choice too.

    The RPC services binds to the localhost loopback network interface, so use rpcbind to change where to bind to and rpcallowip to whitelist source IP access.


    All RPC methods are exposed on the client interface as a camelcase'd version of those available on syscoind.

    For a more complete reference about which methods are available, check the RPC documentation on the Syscoin Core Developer Reference website.

    client.createRawTransaction([{ txid: '1eb590cd06127f78bf38ab4140c4cdce56ad9eb8886999eb898ddf4d3b28a91d', vout: 0 }], { 'mgnucj8nYqdrPFh2JfZSB1NmUThUGnmsqe': 0.13 });
    client.sendMany('test1', { mjSk1Ny9spzU2fouzYgLqGUD8U41iR35QN: 0.1, mgnucj8nYqdrPFh2JfZSB1NmUThUGnmsqe: 0.2 }, 6, 'Example Transaction');
    client.sendToAddress('mmXgiR6KAhZCyQ8ndr2BCfEq1wNG2UnyG6', 0.1,  'sendtoaddress example', 'Nemo From Example.com');

    Batch requests

    Batched requests are support by passing an array to the command method with a method and optionally, parameters. The return value will be an array with all the responses.

    const batch = [
      { method: 'getnewaddress', parameters: [] },
      { method: 'getnewaddress', parameters: [] }
    new Client().command(batch).then((responses) => console.log(responses)));
    // Or, using ES2015 destructuring.
    new Client().command(batch).then(([firstAddress, secondAddress]) => console.log(firstAddress, secondAddress)));

    Note that batched requests will only throw an error if the batch request itself cannot be processed. However, each individual response may contain an error akin to an individual request.

    const batch = [
      { method: 'foobar', params: [] },
      { method: 'getnewaddress', params: [] }
    new Client().command(batch).then(([address, error]) => console.log(address, error)));
    // => `mkteeBFmGkraJaWN5WzqHCjmbQWVrPo5X3, { [RpcError: Method not found] message: 'Method not found', name: 'RpcError', code: -32601 }`.


    Support for the REST interface is still experimental and the API is still subject to change. These endpoints are also unauthenticated so there are certain risks which you should be aware, specifically of leaking sensitive data of the node if not correctly protected.

    Error handling is still fragile so avoid passing user input.

    Start the syscoind with the REST server enabled:

    docker run --rm -it seegno/syscoind:0.12-alpine -printtoconsole -server -rest

    These configuration values may also be set on the syscoin.conf file of your platform installation. Use txindex=1 if you'd like to enable full transaction query support (note: this will take a considerable amount of time on the first run).


    getBlockByHash(hash, [options], [callback])

    Given a block hash, returns a block, in binary, hex-encoded binary or JSON formats.

    1. hash (string): The block hash.
    2. [options] (Object): The options object.
    3. [options.extension=json] (string): Return in binary (bin), hex-encoded binary (hex) or JSON (json) format.
    4. [callback] (Function): An optional callback, otherwise a Promise is returned.
    client.getBlockByHash('0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206', { extension: 'json' });

    getBlockHeadersByHash(hash, count, [options][, callback])

    Given a block hash, returns amount of block headers in upward direction.

    1. hash (string): The block hash.
    2. count (number): The number of blocks to count in upward direction.
    3. [options] (Object): The options object.
    4. [options.extension=json] (string): Return in binary (bin), hex-encoded binary (hex) or JSON (json) format.
    5. [callback] (Function): An optional callback, otherwise a Promise is returned.
    client.getBlockHeadersByHash('0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206', 1, { extension: 'json' });


    Returns various state info regarding block chain processing.


    1. [callback] (Function): An optional callback, otherwise a Promise is returned.


    Returns transactions in the transaction memory pool.


    1. [callback] (Function): An optional callback, otherwise a Promise is returned.


    Returns various information about the transaction memory pool. Only supports JSON as output format.

    • size: the number of transactions in the transaction memory pool.
    • bytes: size of the transaction memory pool in bytes.
    • usage: total transaction memory pool memory usage.


    1. [callback] (Function): An optional callback, otherwise a Promise is returned.

    getTransactionByHash(hash, [options], [callback])

    Given a transaction hash, returns a transaction in binary, hex-encoded binary, or JSON formats.


    1. hash (string): The transaction hash.
    2. [options] (Object): The options object.
    3. [options.summary=false] (boolean): Whether to return just the transaction hash, thus saving memory.
    4. [options.extension=json] (string): Return in binary (bin), hex-encoded binary (hex) or JSON (json) format.
    5. [callback] (Function): An optional callback, otherwise a Promise is returned.
    client.getTransactionByHash('b4dd08f32be15d96b7166fd77afd18aece7480f72af6c9c7f9c5cbeb01e686fe', { extension: 'json', summary: false });

    getUnspentTransactionOutputs(outpoints, [options], [callback])

    Query unspent transaction outputs (UTXO) for a given set of outpoints. See BIP64 for input and output serialisation.


    1. outpoints (array<Object>|Object): The outpoint to query in the format { id: '<txid>', index: '<index>' }.
    2. [options] (Object): The options object.
    3. [options.extension=json] (string): Return in binary (bin), hex-encoded binary (hex) or JSON (json) format.
    4. [callback] (Function): An optional callback, otherwise a Promise is returned.
      id: '0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206',
      index: 0
    }, {
      id: '0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206',
      index: 1
    }], { extension: 'json' }, [callback])


    This client supports SSL out of the box. Simply pass the SSL public certificate to the client and optionally disable strict SSL checking which will bypass SSL validation (the connection is still encrypted but the server it is connecting to may not be trusted). This is, of course, discouraged unless for testing purposes when using something like self-signed certificates.

    Generating a self-signed certificates for testing purposes

    Please note that the following procedure should only be used for testing purposes.

    Generate an self-signed certificate together with an unprotected private key:

    openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 3650 -nodes

    Connecting via SSL

    On Syscoin Core <0.12, you can start the syscoind RPC server directly with SSL:

    docker run --rm -it -v $(PWD)/ssl:/etc/ssl seegno/syscoind:0.11-alpine -printtoconsole -rpcuser=foo -rpcpassword=bar -rpcssl -rpcsslcertificatechainfile=/etc/ssl/syscoind/cert.pem -rpcsslprivatekeyfile=/etc/ssl/syscoind/key.pem -server

    On Syscoin Core >0.12, use must use stunnel (brew install stunnel or sudo apt-get install stunnel4) or an HTTPS reverse proxy to configure SSL since the built-in support for SSL has been removed. The trade off with stunnel is performance and simplicity versus features, as it lacks more powerful capacities such as Basic Authentication and caching which are standard in reverse proxies.

    You can use stunnel by configuring stunnel.conf with the following service requirements:

    accept = 28332
    connect = 18332
    cert = /etc/ssl/syscoind/cert.pem
    key = /etc/ssl/syscoind/key.pem

    The key option may be omitted if you concatenating your private and public certificates into a single stunnel.pem file.

    On some versions of stunnel it is also possible to start a service using command line arguments. The equivalent would be:

    stunnel -d 28332 -r -p stunnel.pem -P ''

    Then pass the public certificate to the client:

    const Client = require('syscoin-core');
    const fs = require('fs');
    const client = new Client({
      agentOptions: {
        ca: fs.readFileSync('/etc/ssl/syscoind/cert.pem')
      port: 28332,
      ssl: true


    By default, all requests made with syscoin-core are logged using uphold/debugnyan with syscoin-core as the logging namespace.

    Please note that all sensitive data is obfuscated before calling the logger.


    Example output defining the environment variable DEBUG=syscoin-core:

    const client = new Client();
    // {
    //   "name": "syscoin-core",
    //   "hostname": "localhost",
    //   "pid": 57908,
    //   "level": 20,
    //   "request": {
    //     "headers": {
    //       "host": "localhost:8332",
    //       "accept": "application/json"
    //     },
    //     "id": "82cea4e5-2c85-4284-b9ec-e5876c84e67c",
    //     "method": "GET",
    //     "type": "request",
    //     "uri": "http://localhost:8332/rest/tx/b4dd08f32be15d96b7166fd77afd18aece7480f72af6c9c7f9c5cbeb01e686fe.json"
    //   },
    //   "msg": "Making request 82cea4e5-2c85-4284-b9ec-e5876c84e67c to GET http://localhost:8332/rest/tx/b4dd08f32be15d96b7166fd77afd18aece7480f72af6c9c7f9c5cbeb01e686fe.json",
    //   "time": "2017-02-07T14:40:35.020Z",
    //   "v": 0
    // }

    Custom logger

    A custom logger can be passed via the logger option and it should implement bunyan's log levels.


    Currently the test suite is tailored for Docker (including docker-compose) due to the multitude of different syscoind configurations that are required in order to get the test suite passing.

    To test using a local installation of node.js but with dependencies (e.g. syscoind) running inside Docker:

    npm run dependencies
    npm test

    To test using Docker exclusively (similarly to what is done in Travis CI):

    npm run testdocker


    npm version [<newversion> | major | minor | patch] -m "Release %s"




    npm i @syscoinorg/syscoin-core

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