Add server.ping RPC call

.gitignore

@@ -5,6 +5,7 @@ tests/*/__pycache__/
 *.#*
 *#
 *~
+docs/_build
 /build
 /dist
 /electrumx.egg-info

docs/protocol-changes.rst

@@ -58,6 +58,7 @@ New methods
 
   * :func:`blockchain.block.headers`
   * :func:`mempool.get_fee_histogram`
+  * :func:`server.ping`
 
 Deprecated methods
 ------------------

docs/protocol-methods.rst

@@ -745,8 +745,8 @@ Return the address paid to by a UTXO.
 mempool.get_fee_histogram
 -------------------------
 
-  Return a histogram of the fee rates paid by transactions in the
+Return a histogram of the fee rates paid by transactions in the memory
-  memory pool, weighted by transaction size.
+pool, weighted by transaction size.
 
 **Signature**
 
@@ -776,8 +776,8 @@ mempool.get_fee_histogram
 server.add_peer
 ---------------
 
-  This call is intended for a new server to get itself into a server's
+A newly-started server uses this call to get itself into other servers'
-  peers list, and should not be used by wallet clients.
+peers lists.  It sould not be used by wallet clients.
 
 **Signature**
 
@@ -949,6 +949,21 @@ server.peers.subscribe
   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
 --------------
@@ -960,6 +975,9 @@ server.version
   .. 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*
 

server/session.py

@@ -329,6 +329,12 @@ class ElectrumX(SessionBase):
 
         return banner
 
+    def ping(self):
+        '''Serves as a connection keep-alive mechanism and for the client to
+        confirm the server is still responding.
+        '''
+        return None
+
     def server_version(self, client_name=None, protocol_version=None):
         '''Returns the server version as a string.
 
@@ -463,6 +469,7 @@ class ElectrumX(SessionBase):
                 'mempool.get_fee_histogram':
                 controller.mempool_get_fee_histogram,
                 'blockchain.block.headers': self.block_headers,
+                'server.ping': self.ping,
             })
 
         self.electrumx_handlers = handlers