electrumx/docs/protocol-methods.rst

Protocol Methods
================

blockchain.address.get_balance
------------------------------

Return the confirmed and unconfirmed balances of a bitcoin address.

**Signature**

  .. function:: blockchain.address.get_balance(address)
  .. deprecated:: 1.2

  * *address*

    The address as a Base58 string.

**Result**

  See :func:`blockchain.scripthash.get_balance`.

blockchain.address.get_history
------------------------------

Return the confirmed and unconfirmed history of a bitcoin address.

**Signature**

  .. function:: blockchain.address.get_history(address)
  .. deprecated:: 1.2

  * *address*

    The address as a Base58 string.

**Result**

  As for :func:`blockchain.scripthash.get_history`.

blockchain.address.get_mempool
------------------------------

Return the unconfirmed transactions of a bitcoin address.

**Signature**

  .. function:: blockchain.address.get_mempool(address)
  .. deprecated:: 1.2

  * *address*

    The address as a Base58 string.

**Result**

  As for :func:`blockchain.scripthash.get_mempool`.

blockchain.address.listunspent
------------------------------

Return an ordered list of UTXOs sent to a bitcoin address.

**Signature**

  .. function:: blockchain.address.listunspent(address)
  .. deprecated:: 1.2

  * *address*

    The address as a Base58 string.

**Result**

  As for :func:`blockchain.scripthash.listunspent`.

blockchain.address.subscribe
----------------------------

Subscribe to a bitcoin address.

**Signature**

  .. function:: blockchain.address.subscribe(address)
  .. deprecated:: 1.2

  *address*

    The address as a Base58 string.

**Result**

  The :ref:`status <status>` of the address.

**Notifications**

  As this is a subcription, the client will receive a notification
  when the :ref:`status <status>` of the address changes.  Its
  signature is

  .. function:: blockchain.address.subscribe(address, status)

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)

  *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

  *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.

blockchain.block.headers
------------------------

Return a concatenated chunk of block headers from the main chain.

**Signature**

  .. function:: blockchain.block.headers(start_height, count)
  .. versionadded:: 1.2

  *start_height*

    The height of the first header requested, a non-negative integer.

  *count*

    The number of headers requested, a non-negative integer.

**Result**

  A dictionary with the following members:

  * *count*

    The number of headers returned, between zero and the number
    requested.  If the chain has not extended sufficiently far, only
    the available headers will be returned.  If more headers than
    *max* were requested at most *max* will be returned.

  * *hex*

    The binary block headers concatenated together in-order as a
    hexadecimal string.

  * *max*

    The maximum number of headers the server will return in a single
    request.

**Example Response**

::

  {
    "count": 2,
    "hex": "0100000000000000000000000000000000000000000000000000000000000000000000003ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4a29ab5f49ffff001d1dac2b7c010000006fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000982051fd1e4ba744bbbe680e1fee14677ba1a3c3540bf7b1cdb606e857233e0e61bc6649ffff001d01e36299"
     "max": 2016
  }

blockchain.estimatefee
----------------------

Return the estimated transaction fee per kilobyte for a transaction to
be confirmed within a certain number of blocks.

**Signature**

  .. function:: blockchain.estimatefee(number)

  *number*

    The number of blocks to target for confirmation.

**Result**

  The estimated transaction fee in coin units per kilobyte, as a
  floating point number.  If the daemon does not have enough
  information to make an estimate, the integer ``-1`` is returned.

**Example Result**

::

  0.00101079

blockchain.headers.subscribe
----------------------------

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

**Signature**

  .. function:: blockchain.headers.subscribe(raw=False)
  .. versionchanged:: 1.2
     Optional *raw* parameter added.

  * *raw*

    :const:`False` or :const:`True`.  The value :const:`False` is
    deprecated.

**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:

    .. function:: blockchain.headers.subscribe(header)

    * *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()

  *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)

blockchain.relayfee
-------------------

Return the minimum fee a low-priority transaction must pay in order to
be accepted to the daemon's memory pool.

**Signature**

  .. function:: blockchain.relayfee()

**Result**

  The fee in whole coin units (BTC, not satoshis for Bitcoin) as a
  floating point number.

**Example Results**

::

   1e-05

::

   0.0

blockchain.scripthash.get_balance
---------------------------------

Return the confirmed and unconfirmed balances of a :ref:`script hash
<script hashes>`.

**Signature**

  .. function:: blockchain.scripthash.get_balance(scripthash)
  .. versionadded:: 1.1

  *scripthash*

    The script hash as a hexadecimal string.

**Result**

  A dictionary with keys `confirmed` and `unconfirmed`.  The value of
  each is the appropriate balance in coin units as a string.

**Result Example**

::

  {
    "confirmed": "1.03873966",
    "unconfirmed": "0.236844"
  }

blockchain.scripthash.get_history
---------------------------------

Return the confirmed and unconfirmed history of a :ref:`script hash
<script hashes>`.

**Signature**

  .. function:: blockchain.scripthash.get_history(scripthash)
  .. versionadded:: 1.1

  *scripthash*

    The script hash as a hexadecimal string.

**Result**

  A list of confirmed transactions in blockchain order, with the
  output of :func:`blockchain.scripthash.get_mempool` appended to the
  list.  Each confirmed transaction is a dictionary with the following
  keys:

  * *height*

    The integer height of the block the transaction was confirmed in.

  * *tx_hash*

    The transaction hash in hexadecimal.

  See :func:`blockchain.scripthash.get_mempool` for how mempool
  transactions are returned.

**Result Examples**

::

  [
    {
      "height": 200004,
      "tx_hash": "acc3758bd2a26f869fcc67d48ff30b96464d476bca82c1cd6656e7d506816412"
    },
    {
      "height": 215008,
      "tx_hash": "f3e1bf48975b8d6060a9de8884296abb80be618dc00ae3cb2f6cee3085e09403"
    }
  ]

::

  [
    {
      "fee": 20000,
      "height": 0,
      "tx_hash": "9fbed79a1e970343fcd39f4a2d830a6bde6de0754ed2da70f489d0303ed558ec"
    }
  ]

blockchain.scripthash.get_mempool
---------------------------------

Return the unconfirmed transactions of a :ref:`script hash <script
hashes>`.

**Signature**

  .. function:: blockchain.scripthash.get_mempool(scripthash)
  .. versionadded:: 1.1

  *scripthash*

    The script hash as a hexadecimal string.

**Result**

  A list of mempool transactions in arbitrary order.  Each mempool
  transaction is a dictionary with the following keys:

  * *height*

    ``0`` if all inputs are confirmed, and ``-1`` otherwise.

  * *tx_hash*

    The transaction hash in hexadecimal.

  * *fee*

    The transaction fee in minimum coin units (satoshis).

**Result Example**

::

  [
    {
      "tx_hash": "45381031132c57b2ff1cbe8d8d3920cf9ed25efd9a0beb764bdb2f24c7d1c7e3",
      "height": 0,
      "fee": 24310
    }
  ]

blockchain.scripthash.listunspent
---------------------------------

Return an ordered list of UTXOs sent to a script hash.

**Signature**

  .. function:: blockchain.scripthash.listunspent(scripthash)
  .. versionadded:: 1.1

  *scripthash*

    The script hash as a hexadecimal string.

**Result**

  A list of unspent outputs in blockchain order.  This function takes
  the mempool into account.  Mempool transactions paying to the
  address are included at the end of the list in an undefined order.
  Any output that is spent in the mempool does not appear.  Each
  output is a dictionary with the following keys:

  * *height*

    The integer height of the block the transaction was confirmed in.
    ``0`` if the transaction is in the mempool.

  * *tx_pos*

    The zero-based index of the output in the transaction's list of
    outputs.

  * *tx_hash*

    The output's transaction hash as a hexadecimal string.

  * *value*

    The output's value in minimum coin units (satoshis).

**Result Example**

::

  [
    {
      "tx_pos": 0,
      "value": 45318048,
      "tx_hash": "9f2c45a12db0144909b5db269415f7319179105982ac70ed80d76ea79d923ebf",
      "height": 437146
    },
    {
      "tx_pos": 0,
      "value": 919195,
      "tx_hash": "3d2290c93436a3e964cfc2f0950174d8847b1fbe3946432c4784e168da0f019f",
      "height": 441696
    }
  ]

blockchain.scripthash.subscribe
-------------------------------

Subscribe to a script hash.

**Signature**

  .. function:: blockchain.scripthash.subscribe(scripthash)
  .. versionadded:: 1.1

  *scripthash*

    The script hash as a hexadecimal string.

**Result**

  The :ref:`status <status>` of the script hash.

**Notifications**

  As this is a subcription, the client will receive a notification
  when the :ref:`status <status>` of the script hash changes.  Its
  signature is

  .. function:: blockchain.scripthash.subscribe(address, status)

blockchain.transaction.broadcast
--------------------------------

Broadcast a transaction to the network.

**Signature**

  .. function:: blockchain.transaction.broadcast(raw_tx)
  .. versionchanged:: 1.1
     errors returned as JSON RPC errors rather than as a result.

  *raw_tx*

    The raw transaction as a hexadecimal string.

**Result**

  The transaction hash as a hexadecimal string.

  **Note** protocol version 1.0 (only) does not respond according to
  the JSON RPC specification if an error occurs.  If the daemon
  rejects the transaction, the result is the error message string from
  the daemon, as if the call were successful.  The client needs to
  determine if an error occurred by comparing the result to the
  expected transaction hash.

**Result Examples**

::

   "a76242fce5753b4212f903ff33ac6fe66f2780f34bdb4b33b175a7815a11a98e"

Protocol version 1.0 returning an error as the result:

::

  "258: txn-mempool-conflict"

blockchain.transaction.get
--------------------------

Return a raw transaction.

**Signature**

  .. function:: blockchain.transaction.get(tx_hash, verbose=False)
  .. versionchanged:: 1.1
     ignored argument *height* removed
  .. versionchanged:: 1.2
     *verbose* argument added

  *tx_hash*

    The transaction hash as a hexadecimal string.

  *verbose*

    Whether a verbose coin-specific response is required.

**Result**

    If *verbose* is :const:`False`, the raw transaction as a
    hexadecimal string.  If :const:`True`, the result is coin-specific
    and whatever the coin daemon returns when asked for a verbose form
    of the raw transaction.

**Example Results**

When *verbose* is :const:`False`::

  "01000000015bb9142c960a838329694d3fe9ba08c2a6421c5158d8f7044cb7c48006c1b48"
  "4000000006a4730440220229ea5359a63c2b83a713fcc20d8c41b20d48fe639a639d2a824"
  "6a137f29d0fc02201de12de9c056912a4e581a62d12fb5f43ee6c08ed0238c32a1ee76921"
  "3ca8b8b412103bcf9a004f1f7a9a8d8acce7b51c983233d107329ff7c4fb53e44c855dbe1"
  "f6a4feffffff02c6b68200000000001976a9141041fb024bd7a1338ef1959026bbba86006"
  "4fe5f88ac50a8cf00000000001976a91445dac110239a7a3814535c15858b939211f85298"
  "88ac61ee0700"

When *verbose* is :const:`True`::

 {
   "blockhash": "0000000000000000015a4f37ece911e5e3549f988e855548ce7494a0a08b2ad6",
   "blocktime": 1520074861,
   "confirmations": 679,
   "hash": "36a3692a41a8ac60b73f7f41ee23f5c917413e5b2fad9e44b34865bd0d601a3d",
   "hex": "01000000015bb9142c960a838329694d3fe9ba08c2a6421c5158d8f7044cb7c48006c1b484000000006a4730440220229ea5359a63c2b83a713fcc20d8c41b20d48fe639a639d2a8246a137f29d0fc02201de12de9c056912a4e581a62d12fb5f43ee6c08ed0238c32a1ee769213ca8b8b412103bcf9a004f1f7a9a8d8acce7b51c983233d107329ff7c4fb53e44c855dbe1f6a4feffffff02c6b68200000000001976a9141041fb024bd7a1338ef1959026bbba860064fe5f88ac50a8cf00000000001976a91445dac110239a7a3814535c15858b939211f8529888ac61ee0700",
   "locktime": 519777,
   "size": 225,
   "time": 1520074861,
   "txid": "36a3692a41a8ac60b73f7f41ee23f5c917413e5b2fad9e44b34865bd0d601a3d",
   "version": 1,
   "vin": [ {
     "scriptSig": {
       "asm": "30440220229ea5359a63c2b83a713fcc20d8c41b20d48fe639a639d2a8246a137f29d0fc02201de12de9c056912a4e581a62d12fb5f43ee6c08ed0238c32a1ee769213ca8b8b[ALL|FORKID] 03bcf9a004f1f7a9a8d8acce7b51c983233d107329ff7c4fb53e44c855dbe1f6a4",
       "hex": "4730440220229ea5359a63c2b83a713fcc20d8c41b20d48fe639a639d2a8246a137f29d0fc02201de12de9c056912a4e581a62d12fb5f43ee6c08ed0238c32a1ee769213ca8b8b412103bcf9a004f1f7a9a8d8acce7b51c983233d107329ff7c4fb53e44c855dbe1f6a4"
     },
     "sequence": 4294967294,
     "txid": "84b4c10680c4b74c04f7d858511c42a6c208bae93f4d692983830a962c14b95b",
     "vout": 0}],
   "vout": [ { "n": 0,
              "scriptPubKey": { "addresses": [ "12UxrUZ6tyTLoR1rT1N4nuCgS9DDURTJgP"],
                                "asm": "OP_DUP OP_HASH160 1041fb024bd7a1338ef1959026bbba860064fe5f OP_EQUALVERIFY OP_CHECKSIG",
                                "hex": "76a9141041fb024bd7a1338ef1959026bbba860064fe5f88ac",
                                "reqSigs": 1,
                                "type": "pubkeyhash"},
              "value": 0.0856647},
            { "n": 1,
              "scriptPubKey": { "addresses": [ "17NMgYPrguizvpJmB1Sz62ZHeeFydBYbZJ"],
                                "asm": "OP_DUP OP_HASH160 45dac110239a7a3814535c15858b939211f85298 OP_EQUALVERIFY OP_CHECKSIG",
                                "hex": "76a91445dac110239a7a3814535c15858b939211f8529888ac",
                                "reqSigs": 1,
                                "type": "pubkeyhash"},
              "value": 0.1360904}]}

blockchain.transaction.get_merkle
---------------------------------

Return the markle branch to a confirmed transaction given its hash
and height.

**Signature**

  .. function:: blockchain.transaction.get_merkle(tx_hash, height)

  *tx_hash*

    The transaction hash as a hexadecimal string.

  *height*

    The height at which it was confirmed, an integer.

**Result**

  A dictionary with the following keys:

  * *block_height*

    The height of the block the transaction was confirmed in.

  * *merkle*

    A list of transaction hashes the current hash is paired with,
    recursively, in order to trace up to obtain merkle root of the
    block, deepest pairing first.

  * *pos*

    The 0-based index of the position of the transaction in the
    ordered list of transactions in the block.

**Result Example**

::

  {
    "merkle":
    [
      "713d6c7e6ce7bbea708d61162231eaa8ecb31c4c5dd84f81c20409a90069cb24",
      "03dbaec78d4a52fbaf3c7aa5d3fccd9d8654f323940716ddf5ee2e4bda458fde",
      "e670224b23f156c27993ac3071940c0ff865b812e21e0a162fe7a005d6e57851",
      "369a1619a67c3108a8850118602e3669455c70cdcdb89248b64cc6325575b885",
      "4756688678644dcb27d62931f04013254a62aeee5dec139d1aac9f7b1f318112",
      "7b97e73abc043836fd890555bfce54757d387943a6860e5450525e8e9ab46be5",
      "61505055e8b639b7c64fd58bce6fc5c2378b92e025a02583303f69930091b1c3",
      "27a654ff1895385ac14a574a0415d3bbba9ec23a8774f22ec20d53dd0b5386ff",
      "5312ed87933075e60a9511857d23d460a085f3b6e9e5e565ad2443d223cfccdc",
      "94f60b14a9f106440a197054936e6fb92abbd69d6059b38fdf79b33fc864fca0",
      "2d64851151550e8c4d337f335ee28874401d55b358a66f1bafab2c3e9f48773d"
    ],
    "block_height": 450538,
    "pos": 710
  }

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.

mempool.get_fee_histogram
-------------------------

Return a histogram of the fee rates paid by transactions in the memory
pool, weighted by transaction size.

**Signature**

  .. function:: mempool.get_fee_histogram()
  .. versionadded:: 1.2

**Result**

  The histogram is an array of [*fee*, *vsize*] pairs, where |vsize_n|
  is the cumulative virtual size of mempool transactions with a fee rate
  in the interval [|fee_n1|, |fee_n|], and |fee_n1| > |fee_n|.

  .. |vsize_n| replace:: vsize\ :sub:`n`
  .. |fee_n| replace:: fee\ :sub:`n`
  .. |fee_n1| replace:: fee\ :sub:`n-1`

  Fee intervals may have variable size.  The choice of appropriate
  intervals is currently not part of the protocol.

**Example Result**

  ::

    [[12, 128812], [4, 92524], [2, 6478638], [1, 22890421]]


server.add_peer
---------------

A newly-started server uses this call to get itself into other servers'
peers lists.  It sould not be used by wallet clients.

**Signature**

  .. function:: server.add_peer(features)

  .. versionadded:: 1.1

  * *features*

    The same information that a call to the sender's
    :func:`server.features` RPC call would return.

**Result**

  A boolean indicating whether the request was tentatively accepted.
  The requesting server will appear in :func:`server.peers.subscribe`
  when further sanity checks complete successfully.


server.banner
-------------

Return a banner to be shown in the Electrum console.

**Signature**

  .. function:: server.banner()

**Result**

  A string.

**Example Result**

  ::

     "Welcome to Electrum!"


server.donation_address
-----------------------

Return a server donation address.

**Signature**

  .. function:: server.donation_address()

**Result**

  A string.

**Example Result**

  ::

     "1BWwXJH3q6PRsizBkSGm2Uw4Sz1urZ5sCj"


server.features
---------------

Return a list of features and services supported by the server.

**Signature**

  .. function:: server.features()

**Result**

  A dictionary of keys and values.  Each key represents a feature or
  service of the server, and the value gives additional information.

  The following features MUST be reported by the server.  Additional
  key-value pairs may be returned.

  * *hosts*

    A dictionary, keyed by host name, that this server can be reached
    at.  Normally this will only have a single entry; other entries
    can be used in case there are other connection routes (e.g. Tor).

    The value for a host is itself a dictionary, with the following
    optional keys:

    * *ssl_port*

      An integer.  Omit or set to :const:`null` if SSL connectivity
      is not provided.

    * *tcp_port*

      An integer.  Omit or set to :const:`null` if TCP connectivity is
      not provided.

    A server should ignore information provided about any host other
    than the one it connected to.

  * *genesis_hash*

    The hash of the genesis block.  This is used to detect if a peer
    is connected to one serving a different network.

  * *hash_function*

    The hash function the server uses for :ref:`script hashing
    <script hashes>`.  The client must use this function to hash
    pay-to-scripts to produce script hashes to send to the server.
    The default is "sha256".  "sha256" is currently the only
    acceptable value.

  * *server_version*

    A string that identifies the server software.  Should be the same
    as the result to the :func:`server.version` RPC call.

  * *protocol_max*
  * *protocol_min*

    Strings that are the minimum and maximum Electrum protocol
    versions this server speaks.  Example: "1.1".

  * *pruning*

    An integer, the pruning limit.  Omit or set to :const:`null` if
    there is no pruning limit.  Should be the same as what would
    suffix the letter ``p`` in the IRC real name.

**Example Result**

::

  {
      "genesis_hash": "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943",
      "hosts": {"14.3.140.101": {"tcp_port": 51001, "ssl_port": 51002}},
      "protocol_max": "1.0",
      "protocol_min": "1.0",
      "pruning": null,
      "server_version": "ElectrumX 1.0.17",
      "hash_function": "sha256"
  }


server.peers.subscribe
----------------------

  Return a list of peer servers.  Despite the name this is not a
  subscription and the server must send no notifications.

**Signature**

  .. function:: server.peers.subscribe()

**Result**

  An array of peer servers, each returned as a 3-element array.  For
  example::

    ["107.150.45.210",
     "e.anonyhost.org",
     ["v1.0", "p10000", "t", "s995"]]

  The first element is the IP address, the second is the host name
  (which might also be an IP address), and the third is a list of
  server features.  Each feature and starts with a letter.  'v'
  indicates the server maximum protocol version, 'p' its pruning limit
  and is omitted if it does not prune, 't' is the TCP port number, and
  's' is the SSL port number.  If a port is not given for 's' or 't'
  the default port for the coin network is implied.  If 's' or 't' is
  missing then the server does not support that transport.

server.ping
-----------

Ping the server to ensure it is responding, and to keep the session
alive.  The server may disconnect clients that have sent no requests
for roughly 10 minutes.

**Signature**

  .. function:: server.ping()
  .. versionadded:: 1.2

**Result**

  Returns :const:`null`.

server.version
--------------

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

**Signature**

  .. function:: server.version(client_name="", protocol_version="1.1")
  .. versionchanged:: 1.1
     *protocol_version* is not ignored.
  .. versionchanged:: 1.2
     Use :func:`server.ping` rather than sending version requests as a
     ping mechanism.

  * *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"