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Searching in: Trouble Reports
ID: TR02S10075
Added on: 2021-02-15
Last update: 2021-02-16
Affects: 7
Due to be solved in:  7
Platform: All Platforms
Product: NoMachine Server
Severity: Minor
Status: Open
Unexpected behaviour of the client when the port bound by MDNS is already in use

Multiple behaviours have been reported when the service to discover other computers in the network is enabled (default) and the port bound by the NoMachine MDNS service was already in use

In some cases, the NoMachine User Interface suddenly terminated as soon as the UI was opened. For example when 'Show the server status' was clicked in the NoMachine menu (open it by clicking on the !M icon in the system tray).

In other cases, MDNS errors like the following flooded the session file but the UI didn't terminate:

10911 10911 22:59:26 233.710 RecentModel: Initializing recent connection providers. 10911 10924 22:59:26 236.863 RecentManagerDiscovery: WARNING! MDNS query finished too early, going to wait for '30000' ms. 10911 10924 22:59:26 238.278 Io/Io: WARNING! Replacing descriptor FD#0 in method 'pipe' context [A]. 10911 10924 22:59:26 238.373 System: Setting system error state to 9. 10911 10924 22:59:26 238.395 Io/Io: WARNING! Close for FD#0 failed. 10911 10924 22:59:26 238.616 Io/Io: WARNING! Error is 9, 'Bad file descriptor'.

Despite of different symptoms, the analysis of these two cases lead to the same root cause, i.e. that the port bound by the NoMachine MDNS service was already in use.

As a workaround disable MDNS discovery in the client configuration.

If the UI doesn't start or suddenly terminates, open the file:


on the client machine and change the value of key: "Discover other NoMachine servers in the network" to "false", i.e.: 

<option key="Discover other NoMachine servers in the network" value="false" />

Then start again the client or the UI.

If  the UI is operative but logs are flooded with MDNS message, you can disable MDNS discovery via interface: launch the UI -> Settings -> Player -> Security and check 'Don't show other computers on the local network'.

Close and restart the UI.

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