fix(src): send messages using correct socket, closes #72

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixed
+
+- Messages are sent via the correct socket to comply with the intended/specified message flow. This also eases the firewall configuration (#72).
+
 ## [0.6.2] - 2020-10-18
 
 ### Changed

README.md

@@ -106,7 +106,8 @@ actual distribution/installation where they are to be used.
 
 Both incoming and outgoing multicast traffic on port 3702 must be allowed. For
 IPv4, the multicast address is `239.255.255.250`, for IPv6 the link local SSDP
-multicast address (`ff02::c`) is used.
+multicast address (`ff02::c`) is used. Outgoing unicast UDP traffic from port
+3702 must be allowed too.
 
 Incoming TCP traffic (and related outgoing traffic) on port 5357 must be
 allowed.

man/wsdd.1

@@ -136,7 +136,8 @@ domain socket to which a client can connect to.
 .PP
 Both incoming and outgoing multicast traffic on port 3702 must be allowed. For
 IPv4, the multicast address is `239.255.255.250`, for IPv6 the link local SSDP
-multicast address (`fe02::c`) is used.
+multicast address (`fe02::c`) is used. Outgoing unicast UDP traffic from port
+3702 must be allowed too.
 .PP
 Incoming TCP traffic (and related outgoing traffic) on port 5357 must be
 allowed.

src/wsdd.py

@@ -183,6 +183,15 @@ def handle_request(self, key):
             for handler in self.message_handlers[s]:
                 handler.handle_request(msg, address)
 
+    def send(self, msg, addr):
+        # Request from a client must be answered from a socket that is bound
+        # to the WSD port, i.e. the recv_socket. Messages to multicast
+        # addresses are sent over the dedicated send socket.
+        if addr == self.multicast_address:
+            self.send_socket.sendto(msg, addr)
+        else:
+            self.recv_socket.sendto(msg, addr)
+
 
 # constants for WSD XML/SOAP parsing
 WSA_URI = 'http://schemas.xmlsoap.org/ws/2004/08/addressing'
@@ -1536,7 +1545,7 @@ def send_outstanding_messages(block=False):
         addr = send_queue[-1][2]
         msg = send_queue[-1][3]
         try:
-            mch.send_socket.sendto(msg, addr)
+            mch.send(msg, addr)
         except Exception as e:
             logger.error('error while sending packet on {}: {}'.format(
                 mch.interface.name, e))