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Removed Protocol Methods

This documents protocol methods that are still supported in some protocol versions, but not the most recent one.

Deserialized Headers

A :dfn:`deserialized header` is a dictionary describing a block at a given height.

A typical example would be similar to this template:

{
  "block_height": <integer>,
  "version": <integer>,
  "prev_block_hash": <hexadecimal string>,
  "merkle_root":  <hexadecimal string>,
  "timestamp": <integer>,
  "bits": <integer>,
  "nonce": <integer>
}

Note

The precise format of a deserialized block header varies by coin, and also potentially by height for the same coin. Detailed knowledge of the meaning of a block header is neither necessary nor appropriate in the server. Consequently they were removed from the protocol in version 1.4.

blockchain.headers.subscribe

Subscribe to receive block headers when a new block is found.

Signature

.. versionchanged:: 1.2
   Optional *raw* parameter added, defaulting to :const:`false`.

.. versionchanged:: 1.3
   *raw* parameter deafults to :const:`true`.

.. versionchanged:: 1.4
   *raw* parameter removed; responses and notifications pass raw
   headers.

  • raw

    This single boolean argument exists in protocol versions 1.2 (defaulting to :const:`false`) and 1.3 (defaulting to :const:`true`) only.

Result

The header of the current block chain tip. If raw is :const:`true` the result is a dictionary with two members:

  • hex

    The binary header as a hexadecimal string.

  • height

    The height of the header, an integer.

If raw is :const:`false` the result is the coin-specific :ref:`deserialized header <deserialized header>`.

Example Result

With raw :const:`false`:

{
  "bits": 402858285,
  "block_height": 520481,
  "merkle_root": "8e8e932eb858fd53cf09943d7efc9a8f674dc1363010ee64907a292d2fb0c25d",
  "nonce": 3288656012,
  "prev_block_hash": "000000000000000000b512b5d9fc7c5746587268547c04aa92383aaea0080289",
  "timestamp": 1520495819,
  "version": 536870912
}

With raw :const:`true`:

{
  "height": 520481,
  "hex": "00000020890208a0ae3a3892aa047c5468725846577cfcd9b512b50000000000000000005dc2b02f2d297a9064ee103036c14d678f9afc7e3d9409cf53fd58b82e938e8ecbeca05a2d2103188ce804c4"
}

Notifications

As this is a subcription, the client will receive a notification when a new block is found. The notification's signature is:

  • header

    See Result above.

Note

should a new block arrive quickly, perhaps while the server is still processing prior blocks, the server may only notify of the most recent chain tip. The protocol does not guarantee notification of all intermediate block headers.

In a similar way the client must be prepared to handle chain reorganisations. Should a re-org happen the new chain tip will not sit directly on top of the prior chain tip. The client must be able to figure out the common ancestor block and request any missing block headers to acquire a consistent view of the chain state.

blockchain.numblocks.subscribe

Subscribe to receive the block height when a new block is found.

Signature

.. function:: blockchain.numblocks.subscribe()

.. deprecated:: 1.0 removed in version 1.1

Result

The height of the current block, an integer.

Notifications

As this is a subcription, the client will receive a notification when a new block is found. The notification's signature is:

.. function:: blockchain.numblocks.subscribe(height)
   :noindex:

blockchain.utxo.get_address

Return the address paid to by a UTXO.

Signature

.. function:: blockchain.utxo.get_address(tx_hash, index)

  *Optional in version 1.0, removed in version 1.1*

tx_hash

The transaction hash as a hexadecimal string.

index

The zero-based index of the UTXO in the transaction.

Result

A Base58 address string, or :const:`null`. If the transaction doesn't exist, the index is out of range, or the output is not paid to an address, :const:`null` must be returned. If the output is spent :const:`null` may be returned.

blockchain.block.get_header

Return the :ref:`deserialized header <deserialized header>` of the block at the given height.

Signature

.. function:: blockchain.block.get_header(height)

.. deprecated:: 1.3 removed in version 1.4

height

The height of the block, an integer.

Result

The coin-specific :ref:`deserialized header <deserialized header>`.

Example Result

{
  "bits": 392292856,
  "block_height": 510000,
  "merkle_root": "297cfcc6a66e063692b20650d21cc0ac7a2a80f7277ebd7c5d6c7010a070d25c",
  "nonce": 3347656422,
  "prev_block_hash": "0000000000000000002292de0d9f03dfa15a04dbf09102d5d4552117b717fa86",
  "timestamp": 1519083654,
  "version": 536870912
}

blockchain.block.get_chunk

Return a concatenated chunk of block headers from the main chain. Typically, a chunk consists of a fixed number of block headers over which difficulty is constant, and at the end of which difficulty is retargeted.

In the case of Bitcoin a chunk is 2,016 headers, each of 80 bytes, so chunk 5 consists of the block headers from height 10,080 to 12,095 inclusive. When encoded as hexadecimal, the result string is twice as long, so for Bitcoin it takes 322,560 bytes, making this a bandwidth-intensive request.

Signature

.. function:: blockchain.block.get_chunk(index)

.. deprecated:: 1.2 removed in version 1.4

index

The zero-based index of the chunk, an integer.

Result

The binary block headers as hexadecimal strings, in-order and concatenated together. As many as headers as are available at the implied starting height will be returned; this may range from zero to the coin-specific chunk size.

server.version

Identify the client to the server and negotiate the protocol version.

Signature

.. versionchanged:: 1.1
   *protocol_version* is not ignored.

.. versionchanged:: 1.2
   Use :func:`server.ping` rather than sending version requests as a
   ping mechanism.

.. versionchanged:: 1.4
   Only the first :func:`server.version` message is accepted.

  • client_name

    A string identifying the connecting client software.

  • protocol_version

    An array [protocol_min, protocol_max], each of which is a string. If protocol_min and protocol_max are the same, they can be passed as a single string rather than as an array of two strings, as for the default value.

The server should use the highest protocol version both support:

version = min(client.protocol_max, server.protocol_max)

If this is below the value:

max(client.protocol_min, server.protocol_min)

then there is no protocol version in common and the server must close the connection. Otherwise it should send a response appropriate for that protocol version.

Result

An array of 2 strings:

[server_software_version, protocol_version]

identifying the server and the protocol version that will be used for future communication.

Protocol version 1.0: A string identifying the server software.

Examples:

server.version("Electrum 3.0.6", ["1.1", "1.2"])
server.version("2.7.1", "1.0")

Example Results:

["ElectrumX 1.2.1", "1.2"]
"ElectrumX 1.2.1"