Add python based subscription clients

data/subscribe-block.py

@@ -0,0 +1,24 @@
+#!python3
+import sys
+import zmq
+import struct
+from binascii import hexlify, unhexlify
+
+# Connect to the public block service.
+url = 'tcp://mainnet.libbitcoin.net:9093'
+if len(sys.argv) > 1:
+    url = sys.argv[1]
+
+context = zmq.Context()
+socket = context.socket(zmq.SUB)
+socket.connect(url)
+socket.setsockopt(zmq.SUBSCRIBE, '')
+
+while True:
+    # Collect the response in parts.
+    sequence = struct.unpack('<H', socket.recv())[0]
+    height = struct.unpack('<I', socket.recv())[0]
+    block_data = hexlify(socket.recv()).decode('ascii')
+
+    print '[Seq:{}] Block {} received {}'.format(
+        sequence, height, block_data)

data/subscribe-heartbeat.py

@@ -0,0 +1,22 @@
+#!python3
+import sys
+import zmq
+import struct
+
+# Connect to the public heartbeat service.
+url = 'tcp://mainnet.libbitcoin.net:9092'
+if len(sys.argv) > 1:
+    url = sys.argv[1]
+
+context = zmq.Context()
+socket = context.socket(zmq.SUB)
+socket.connect(url)
+socket.setsockopt(zmq.SUBSCRIBE, '')
+
+while True:
+    # Collect the response in parts.
+    sequence = struct.unpack('<H', socket.recv())[0]
+    height = struct.unpack('<Q', socket.recv())[0]
+
+    print '[Seq:{}] Heartbeat received with height {}'.format(
+        sequence, height)

data/subscribe-tx.py

@@ -0,0 +1,22 @@
+#!python3
+import sys
+import zmq
+import struct
+from binascii import hexlify, unhexlify
+
+# Connect to the public transaction service.
+url = 'tcp://mainnet.libbitcoin.net:9094'
+if len(sys.argv) > 1:
+    url = sys.argv[1]
+
+context = zmq.Context()
+socket = context.socket(zmq.SUB)
+socket.connect(url)
+socket.setsockopt(zmq.SUBSCRIBE, '')
+
+while True:
+    # Collect the response in parts.
+    sequence = struct.unpack('<H', socket.recv())[0]
+    transaction = hexlify(socket.recv()).decode('ascii')
+
+    print '[Seq:{}] Transaction received: {}'.format(sequence, transaction)

src/services/heartbeat_service.cpp

@@ -128,7 +128,7 @@ void heartbeat_service::publish(zmq::socket& publisher)
         return;
 
     // [ sequence:2 ]
-    // [ height:4 ]
+    // [ height:8 ]
     zmq::message message;
     message.enqueue_little_endian(++sequence_);
     message.enqueue_little_endian(node_.top_block().height());