This problem has been reported when running sessions from Windows to Linux server.

It is possible that when running two NX clients which use the same target port to connect to two different servers, e.g., test@hostA:1003 and testnx@hostB:1003, NX Proxy won't allow one of the client sessions to connect, and will more than likely report an error similar to this:

Error: Call to accept failed for font server connection.

or

Error: Call to bind failed for font TCP port 11001. Error is 112 'Address already in use'.

Problem is related to the font server channel. A possible solution is disabling the font channel by adding the option font=0 to the NX proxy on the client ;side.

In order to do this, create a file named options in the directory
%USERPROFILE%.nx

The options file has to be created with a single line like the following:

font=0

without spaces around the equal sign.

More details are available in the following article:

https://www.nomachine.com/AR06E00466

With the font channel disabled, reconnecting sessions on the client could have problems with missing fonts. If this is the case, please install the add-on fonts packages.