handle blank ssdp packets and those with only one line

aioupnp/serialization/ssdp.py

@@ -189,6 +189,8 @@ class SSDPDatagram(object):
     @classmethod
     def _from_string(cls, datagram: str):
         lines = [l for l in datagram.split(line_separator) if l]
+        if not lines:
+            return
         if lines[0] == cls._start_lines[cls._M_SEARCH]:
             return cls._from_request(lines[1:])
         if lines[0] in [cls._start_lines[cls._NOTIFY], cls._start_lines[cls._NOTIFY] + " "]:

tests/serialization/test_ssdp.py

@@ -28,6 +28,18 @@ class TestSSDPDatagram(unittest.TestCase):
         with self.assertRaises(UPnPError):
             SSDPDatagram.decode(packet)
 
+    def test_fail_to_decode_blank(self):
+        packet = b''
+
+        with self.assertRaises(UPnPError):
+            SSDPDatagram.decode(packet)
+
+    def test_fail_to_decode_one_line(self):
+        packet = b'M-SEARCH * HTTP/1.1'
+
+        with self.assertRaises(UPnPError):
+            SSDPDatagram.decode(packet)
+
     def test_cli_args(self):
         datagram_args = OrderedDict([
             ('Host', "{}:{}".format('239.255.255.250', 1900)),

tests/test_gateway.py

@@ -1,5 +1,3 @@
-from aioupnp.fault import UPnPError
-from aioupnp.protocols.scpd import scpd_post, scpd_get
 from tests import TestBase
 from tests.mocks import mock_tcp_endpoint_factory
 from collections import OrderedDict