[FreeNX-kNX] Port Assignment

Thu Mar 12 14:15:36 UTC 2015

John H <lmindnix at gmail.com> Sent by: "FreeNX-kNX" 
<freenx-knx-bounces at kde.org> 11/03/2015 22:33 Please respond to User 
Support for FreeNX Server and kNX Client <freenx-knx at kde.org>

Hey all.  Having issues with TCP port binding on the server from client.  

<SNIP>

Error: Call to bind failed for TCP port 35022. Error is 98 'Address 
already in use'.
Error: Aborting session with 'Unable to open display 
'nx/nx,options=/users/testuser/.nx/C-blade015-31022-B88B9BA2369A5DC1AB0AA53AA52EFC60/options:31022''.

I've seen this discussed in previous threads here:
http://marc.info/?l=freenx-knx&m=138442658819979&w=2

YUP

Checking port 35022 reveals that it's in use by LDAP, bound to a different 
user on that NX server.

YUP - and of course something has to give somewhere

So, we're trying to figure out the best way to change the port, either 
from the client or the server, that would result in a successful login.
Currently, the symptoms are, double-click connection name from NoMachine 
app, it requests password, password success, requests session type (Gnome, 
KDE, etc) and once that session type is selected, it hangs at "Creating 
session".  
I've tried going into the testuser's ~/.nx/config/blade015.nxs and 
changing the NoMachine daemon port from 4000 to 4001, but that doesn't 
seem to have the intended effect as, after having saved the change, then 
closing and re-opening the NoMachine client to reconnect changes that 
value back to 4000.  
I can't change the server variable "DISPLAY_BASE=" because others are 
connected to it, but I feel pretty confident that if/when their connection 
is dropped, they'll be faced with the same issues as our testuser.  

Sounds like you have the 6000 4000 bug in nxserver.

 Can you see:-

                        # Check if there is already an agent running on 
that display on that host
                        let AGENT_DISPLAY=$SESS_DISPLAY+6000
somewhere near line No. 1450 in

                 /usr/bin/nxserver

If you do, try setting 

                let AGENT_DISPLAY=$SESS_DISPLAY+4000

and see if that fixes it ( by skipping over any used ports)

 Please let us know if it works before/after
so
Akemi can update it ( if he's still around and can be bothered )

NOTA BENE  this ** WONT**  stop the reverse problem occuring if someone 
has decided to grab 35022 all the time and finds it's used by FreeNX !!!!

Mostly no one's sessions run into anything else because the default is 
1000 or 2000 3000 etc if you have several FreeNX servers not 35000 or so 
which you seem to have set.

NOTES
------------

The 
        DISPLAY_BASE=

 FreeNX server parameter sets the base number or starting value for that 
FreeNX server, from which the connecting users are allocated in turn, one 
at a time a

         "session display base"

from which various display/port values are calculated by adding a value 
hard wired into the code

eg in original nxserver

SESS_DISPLAY=$DISPLAY_BASE              # used for apps ie the  session 
env $DISPLAY 
let PROXY_DISPLAY=$SESS_DISPLAY+4000    # the one you're (probably) having 
problems with

let AGENT_DISPLAY=$SESS_DISPLAY+6000    # bug should be 4000
let SAMBA_DISPLAY=$SESS_DISPLAY+3000
let MEDIA_DISPLAY=$SESS_DISPLAY+7000
let CUPS_DISPLAY=$SESS_DISPLAY+9000     # bug should be 9090 see below

The four above are part of session set-up test code, only used to see if 
the ports are free - if not then a new SESS_DISPLAY++ is tried 

see in nxnode where it all actually happens

let ESPEAKER=$display+7000
let NXSAMBA_PORT=$display+3000
let NODE_CUPSD_PORT=$display+9090       # should be same as above

In this instance your server's DISPLAY_BASE  is set to something near the 
31022 - maybe 31000 with 21 users already connected from which 4000 is 
added to give the 35022

You might be safer going back to 2000 to keep away from anything else in 
user-land

 NOTE you CAN change the display base because it won't affect any RUNNING 
sessions. You are probably best advised not to restart the "service" tho

"Strangely", this "session display base" number is handed over to the nx 
client  which then uses this same number for its X server ( or client in 
normal speak)
and then builds its connection parameter string to send to the server, 
requesting the value the server just passed over . . . . hence you can't 
change anything via the client . . .

This of course meant if you were connecting to several FreeNX servers at 
the same time, you might find that you got the same number from more that 
one of them, which the client can't accept,
which was the subject of the 2013 forum message you mention, referring to 
the work-around advisory from back in 2008, applicable to simultaneous 
multiple FreeNX sever connections

Good luck anyway

cb

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