agent: known host, smp protocol: parse empty messages (#1953)

Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>

src/Simplex/Messaging/Agent/Client.hs

@@ -1194,10 +1194,10 @@ sendOrProxySMPCommand c nm userId destSrv@ProtocolServer {host = destHosts} conn
       cfg <- getNetworkConfig c
       case smpProxyMode cfg of
         SPMAlways -> pure True
-        SPMUnknown -> unknownServer
+        SPMUnknown -> unknownServer cfg
         SPMUnprotected
           | ipAddressProtected cfg destSrv -> pure False
-          | otherwise -> unknownServer
+          | otherwise -> unknownServer cfg
         SPMNever -> pure False
     directAllowed = do
       cfg <- getNetworkConfig c
@@ -1205,7 +1205,7 @@ sendOrProxySMPCommand c nm userId destSrv@ProtocolServer {host = destHosts} conn
         SPFAllow -> True
         SPFAllowProtected -> ipAddressProtected cfg destSrv
         SPFProhibit -> False
-    unknownServer = liftIO $ maybe True (\srvs -> all (`S.notMember` knownHosts srvs) destHosts) <$> TM.lookupIO userId (smpServers c)
+    unknownServer cfg = liftIO $ maybe True (\srvs -> either (const True) (`S.notMember` knownHosts srvs) $ chooseTransportHost cfg destHosts) <$> TM.lookupIO userId (smpServers c)
     sendViaProxy :: Maybe SMPServerWithAuth -> SMPTransportSession -> AM (Maybe SMPServer, a)
     sendViaProxy proxySrv_ destSess@(_, _, connId_) = do
       r <- tryAllErrors . withProxySession c nm proxySrv_ destSess entId ("PFWD " <> cmdStr) $ \(SMPConnectedClient smp _, proxySess@ProxiedRelay {prBasicAuth}) -> do

src/Simplex/Messaging/Protocol.hs

@@ -884,7 +884,7 @@ instance StrEncoding Message where
       msgQuotaP msgId msgTs = "quota" $> MessageQuota {msgId, msgTs}
       msgP msgId msgTs = do
         msgFlags <- ("flags=" *> strP_) <|> pure noMsgFlags
-        msgBody <- strP
+        msgBody <- strP <|> (C.unsafeMaxLenBS "" <$ A.endOfInput)
         pure Message {msgId, msgTs, msgFlags, msgBody}
 
 type EncNMsgMeta = ByteString