Remote Procedure Calls (RPCs)#

Overview#

Dash Core provides a remote procedure call (RPC) interface for various administrative tasks, wallet operations, and queries about network and block chain data.

Open-source client libraries for the RPC interface are readily available in most modern programming languages, so you probably don’t need to write your own from scratch. Dash Core also ships with its own compiled C++ RPC client, dash-cli, located in the bin directory alongside dashd and dash-qt. The dash-cli program can be used as a command-line interface (CLI) to Dash Core or for making RPC calls from applications written in languages lacking a suitable native client. The remainder of this section describes the Dash Core RPC protocol in detail.

📘 Dash Core Configuration

The following subsections reference setting configuration values. See the Examples Page for more information about setting Dash Core configuration values.

Enabling RPC#

If you start Dash Core using dash-qt, the RPC interface is disabled by default. To enable it, set server=1 in dash.conf or supply the -server argument when invoking the program. If you start Dash Core using dashd, the RPC interface is enabled by default.

Basic Security#

The interface requires the user to provide a password for authenticating RPC requests. This password can be set either using the rpcpassword property in dash.conf or by supplying the -rpcpassword program argument. Optionally a username can be set using the rpcuser configuration value.

RPC-Auth Security#

Alternatively, the authentication details can be provided using the rpcauth property. This removes the need to include a plaintext password in the dash.conf file by instead including a salt and hash of the password along with a username in the format: <USERNAME>:<SALT>$<HASH>

# Example dash.conf rpcauth entry
rpcauth=myuser:933fff1aaefa1fc5b3e981fd3ceacf03$f799757c0d36be8f1faa1dd3a01562b17ada82f2ff6c968c959103afda9e7c6f

📘

The rpcauth option can be specified multiple times if multiple users are required.

A canonical python script is included in Dash Core’s repository under share/rpcuser to generate the information required for the dash.conf file as well as the password required by clients using the rpcauth name.

String to be appended to dash.conf:
rpcauth=myuser:b87393f6957f80448f8a0aba5eb8cc00$f67a3321106b13acc2a8881c9eb64e7bbc6eeb4681261b2918cc54da8915be6e
Your password:
2-Cl0O92-MT-XavyEIkkV_hxqdC_7fag8w7EF7t3UVg=

RPC Whitelist#

The RPC whitelist system can limit certain RPC users to only have access to some RPC calls. The system is configured by specifying the following two parameters in the dash.conf file or by setting them as program arguments on the command line:

rpcwhitelist: set a whitelist to filter incoming RPC calls for a specific user. The field comes in the format: <USERNAME>:<rpc 1>,<rpc 2>,...,<rpc n>. If multiple whitelists are set for a given user, they are set-intersected. Default whitelist behavior is defined by rpcwhitelistdefault.
rpcwhitelistdefault: sets default behavior for RPC whitelisting. Unless rpcwhitelistdefault is set to 0, if any rpcwhitelist is set, the RPC server acts as if all RPC users are subject to empty-unless-otherwise-specified whitelists. If rpcwhitelistdefault is set to 1 and no rpcwhitelist is set, the RPC server acts as if all RPC users are subject to empty whitelists.

Example configuration

rpcauth=user1:4cc74397d6e9972e5ee7671fd241$11849357f26a5be7809c68a032bc2b16ab5dcf6348ef3ed1cf30dae47b8bcc71
rpcauth=user2:181b4a25317bff60f3749adee7d6bca0$d9c331474f1322975fa170a2ffbcb176ba11644211746b27c1d317f265dd4ada
rpcauth=user3:a6c8a511b53b1edcf69c36984985e$13cfba0e626db19061c9d61fa58e712d0319c11db97ad845fa84517f454f6675
rpcwhitelist=user1:getnetworkinfo
rpcwhitelist=user2:getnetworkinfo,getwalletinfo, getbestblockhash

# Allow users to access any RPC unless they are listed in an `rpcwhitelist` entry
rpcwhitelistdefault=0

In this example, user1 can only call getnetworkinfo, user2 can only call getnetworkinfo or getwalletinfo, while user3 can still call all RPCs.

Restricted Access Users#

🚧

This feature is only available on masternodes

As of Dash Core 0.17.0, an option is provided to add an RPC user that is restricted to a small subset of RPCs that will be used by Dash Platform. The platform-user configuration value sets the name of the RPC user to be restricted.

The platform-user configuration value must be set to a previously configured rpcauth user.

Only the following RPCs are accessible to the restricted user:

getbestblockhash
getblockhash
getblockcount
getbestchainlock
quorum sign 4 - The restricted user can only request quorum signatures from the Platform quorum (LLMQ type 4)
quorum verify
verifyislock

Default Connection Info#

The Dash Core RPC service listens for HTTP POST requests on port 9998 in mainnet mode, 19998 in testnet, or 19898 in regression test mode. The port number can be changed by setting rpcport in dash.conf. By default the RPC service binds to your server’s localhost loopback network interface so it’s not accessible from other servers. Authentication is implemented using HTTP basic authentication. RPC HTTP requests must include a Content-Type header set to text/plain and a Content-Length header set to the size of the request body.

Data Formats#

The format of the request body and response data is based on version 1.0 of the JSON-RPC specification.

Request Format#

Specifically, the HTTP POST data of a request must be a JSON object with the following format:

Name	Type	Presence	Description
Request	object	Required (exactly 1)	The JSON-RPC request object
→ `jsonrpc`	number (real)	Optional (0 or 1)	Version indicator for the JSON-RPC request. Currently ignored by Dash Core.
→ `id`	string	Optional (0 or 1)	An arbitrary string that will be returned with the response. May be omitted or set to an empty string (“”)
→ `method`	string	Required (exactly 1)	The RPC method name (e.g. `getblock`). See the RPC section for a list of available methods.
→ `params`	array	Optional (0 or 1)	An array containing positional parameter values for the RPC. May be an empty array or omitted for RPC calls that don’t have any required parameters.
→ `params`	object	Optional (0 or 1)	Starting from Dash Core 0.12.3 / Bitcoin Core 0.14.0 (replaces the params array above) An object containing named parameter values for the RPC. May be an empty object or omitted for RPC calls that don’t have any required parameters.
→ → Parameter	any	Optional (0 or more)	A parameter. May be any JSON type allowed by the particular RPC method

In the table above and in other tables describing RPC input and output, we use the following conventions

“→” indicates an argument that is the child of a JSON array or JSON object. For example, “→ → Parameter” above means Parameter is the child of the params array which itself is a child of the Request object.
Plain-text names like “Request” are unnamed in the actual JSON object
Code-style names like params are literal strings that appear in the JSON object.
“Type” is the JSON data type and the specific Dash Core type.
“Presence” indicates whether or not a field must be present within its containing array or object. Note that an optional object may still have required children.

Response Format#

The HTTP response data for a RPC request is a JSON object with the following format:

Name	Type	Presence	Description
Response	object	Required (exactly 1)	The JSON-RPC response object.
→ `result`	any	Required (exactly 1)	The RPC output whose type varies by call. Has value `null` if an error occurred.
→ `error`	null/object	Required (exactly 1)	An object describing the error if one occurred, otherwise `null`.
→ → `code`	number (int)	Required (exactly 1)	The error code returned by the RPC function call. See rpcprotocol.h for a full list of error codes and their meanings.
→ → `message`	string	Required (exactly 1)	A text description of the error. May be an empty string (“”).
→ `id`	string	Required (exactly 1)	The value of `id` provided with the request. Has value `null` if the `id` field was omitted in the request.

Example#

As an example, here is the JSON-RPC request object for the hash of the genesis block:

{
    "method": "getblockhash",
    "params": [0],
    "id": "foo"
}

The command to send this request using dash-cli is:

dash-cli getblockhash 0

The command to send this request using dash-cli with named parameters is:

dash-cli -named getblockhash height=0

Alternatively, we could POST this request using the cURL command-line program as follows:

curl --user 'my_username:my_secret_password' --data-binary '''
  {
      "method": "getblockhash",
      "params": [0],
      "id": "foo"
  }''' \
  --header 'Content-Type: text/plain;' localhost:9998

The HTTP response data for this request would be:

{
    "result": "00000bafbc94add76cb75e2ec92894837288a481e5c005f6563d91623bf8bc2c",
    "error": null,
    "id": "foo"
}

📘

Note: In order to minimize its size, the raw JSON response from Dash Core doesn’t include any extraneous whitespace characters.

Here whitespace has been added to make the object more readable. dash-cli also transforms the raw response to make it more human-readable. It:

Adds whitespace indentation to JSON objects
Expands escaped newline characters (“\n”) into actual newlines
Returns only the value of the result field if there’s no error
Strips the outer double-quotes around results of type string
Returns only the error field if there’s an error

Continuing with the example above, the output from the dash-cli command would be simply:

00000bafbc94add76cb75e2ec92894837288a481e5c005f6563d91623bf8bc2c

Multi-wallet Support#

Since Dash Core 18.0 introduced the ability to have multiple wallets loaded at the same time, wallet-related RPCs require providing the wallet name when more than one wallet file is loaded. This is to ensure the RPC command is executed using the correct wallet.

Dash-cli Example

Use the dash-cli -rpcwallet option to specify the path of the wallet file to access, for example:

dash-cli -rpcwallet=<wallet-filename> <command>

To use the default wallet, use "" for the wallet filename as shown in the example below:

dash-cli -rpcwallet="" getwalletinfo

JSON-RPC Example

Specify which wallet file to access by setting the HTTP endpoint in the JSON-RPC request using the format <RPC IP address>:<RPC port>/wallet/<wallet name>, for example:

curl --user 'my_username:my_secret_password' --data-binary '''
  {
    "method": "getwalletinfo",
    "params": [],
    "id":"foo"
  }'''\
  --header 'content-type: text/plain;' localhost:19998/wallet/testnet-wallet

Access the default wallet using the format <RPC IP address>:<RPC port>/wallet/ (the final “/” must be included):

curl --user 'my_username:my_secret_password' --data-binary '''
  {
    "method": "getwalletinfo",
    "params": [],
    "id":"foo"
  }'''\
  --header 'content-type: text/plain;' localhost:19998/wallet/

RPCs with sub-commands#

Dash Core has a number of RPC requests that use sub-commands to group access to related data under one RPC method name. Examples of this include the gobject, masternode, protx, and quorum RPCs. If using cURL, the sub-commands should be included in the requests params field as shown here:

curl --user 'my_username:my_secret_password' --data-binary '''
  {
      "method": "gobject",
      "params": ["list", "valid", "proposals"],
      "id": "foo"
  }''' \
  --header 'Content-Type: text/plain;' localhost:9998

Error Handling#

If there’s an error processing a request, Dash Core sets the result field to null and provides information about the error in the error field. For example, a request for the block hash at block height -1 would be met with the following response (again, whitespace added for clarity):

{
    "result": null,
    "error": {
        "code": -8,
        "message": "Block height out of range"
    },
    "id": "foo"
}

If dash-cli encounters an error, it exits with a non-zero status code and outputs the error field as text to the process’s standard error stream:

error code: -8
error message:
Block height out of range

Batch Requests#

The RPC interface supports request batching as described in version 2.0 of the JSON-RPC specification. To initiate multiple RPC requests within a single HTTP request, a client can POST a JSON array filled with Request objects. The HTTP response data is then a JSON array filled with the corresponding Response objects. Depending on your usage pattern, request batching may provide significant performance gains. The dash-cli RPC client does not support batch requests.

curl --user 'my_username:my_secret_password' --data-binary '''
  [
    {
      "method": "getblockhash",
      "params": [0],
      "id": "foo"
    },
    {
      "method": "getblockhash",
      "params": [1],
      "id": "foo2"
    }
  ]''' \
  --header 'Content-Type: text/plain;' localhost:9998

To keep this documentation compact and readable, the examples for each of the available RPC calls will be given as dash-cli commands:

dash-cli [options] <method name> <param1> <param2> ...

This translates into an JSON-RPC Request object of the form:

{
    "method": "<method name>",
    "params": [ "<param1>", "<param2>", "..." ],
    "id": "foo"
}

🚧 High-precision real numbers

Warning: if you write programs using the JSON-RPC interface, you must ensure they handle high-precision real numbers correctly. See the Proper Money Handling Bitcoin Wiki article for details and example code.