frappy-cli: connect to servers on localhost by default

--scan option: specify where to scan if not on localhost

Change-Id: I51a694eb3cb045e7d18c19a332db8e6ba063009b

frappy/protocol/discovery.py

@@ -23,6 +23,9 @@
 import os
 import json
 import socket
+import select
+from time import monotonic
+from collections import namedtuple
 
 from frappy.lib import closeSocket
 from frappy.protocol.interface.tcp import format_address
@@ -32,6 +35,79 @@ UDP_PORT = 10767
 MAX_MESSAGE_LEN = 508
 
 
+Answer = namedtuple('Answer',
+                    'address, hostname, port, equipment_id, firmware, description')
+
+
+def decode(msg, addr):
+    msg = msg.decode('utf-8')
+    try:
+        data = json.loads(msg)
+    except Exception:
+        return None
+    if not isinstance(data, dict):
+        return None
+    if data.get('SECoP') != 'node':
+        return None
+    try:
+        eq_id = data['equipment_id']
+        fw = data['firmware']
+        desc = data['description']
+        port = data['port']
+    except KeyError:
+        return None
+    try:
+        hostname = socket.gethostbyaddr(addr[0])[0]
+    except Exception:
+        hostname = addr[0]
+    return Answer(addr[0], hostname, port, eq_id, fw, desc)
+
+
+def scan(max_wait=1.0):
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+    # send a general broadcast
+    try:
+        s.sendto(json.dumps(dict(SECoP='discover')).encode('utf-8'),
+                 ('255.255.255.255', UDP_PORT))
+    except OSError as e:
+        print('could not send the broadcast:', e)
+        # we still keep listening for self-announcements
+    seen = set()
+    start = monotonic()
+    while monotonic() < start + max_wait:
+        res = select.select([s], [], [], 0.1)
+        if res[0]:
+            try:
+                msg, addr = s.recvfrom(1024)
+            except socket.error:  # pragma: no cover
+                continue
+            answer = decode(msg, addr)
+            if answer is None:
+                continue
+            if (answer.address, answer.equipment_id, answer.port) in seen:
+                continue
+            seen.add((answer.address, answer.equipment_id, answer.port))
+            yield answer
+
+
+def listen():
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    if os.name == 'nt':
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    else:
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    s.bind(('0.0.0.0', UDP_PORT))
+    while True:
+        try:
+            msg, addr = s.recvfrom(1024)
+        except KeyboardInterrupt:
+            break
+        answer = decode(msg, addr)
+        if answer:
+            yield answer
+
+
 class UDPListener:
     def __init__(self, equipment_id, description, ifaces, logger, *,
                  startup_broadcast=True):