Hi, well, of course IPv4 should suffice. Maybe you should check if your name resolution yields IPv6 addresses. No idea how slackware handles this but there should be a straightforward way to disable IPv6. Using firewall rules seems wrong to me.
In RedHat you can do this using sysctl and set "net.ipv6.conf.all.disable_ipv6 = 1". Uli On Mon, Jan 19, 2026 at 11:23 PM Athanasios Silis <[email protected]> wrote: > > Ok I have figured it out, but I don't think it should be like that. > > So I have completely disabled ipv6 on that laptop (policy is DROP for all > chains INPUT, OUTPUT and FORWARD). No it did not even accept localhost > connections in ipv6. > Once I changed the firewall to accept local ipv6 connections (accept from > localhost only and accept OUTgoing packets in output chain) things started > working again. > > The question is. Shouldn't ipv4 suffice for all this to work ? > > This question has no practical value but I would very much like to understand > why does ipv6 must be allowed internally. > > Thank you for your help Ulrich! > > > On Mon, Jan 19, 2026 at 11:03 PM Athanasios Silis > <[email protected]> wrote: >> >> hi Ulrich, >> thank you for the quick response. >> Definitely X11 systems across all the systems I admin - no wayland. >> >> The quick test does indeed create an nxagent window . It does delay >> unreasonably though for about 10seconds at some point. >> Eventually it does continue and I do see the black/empty window eventually. >> You'll notice that the nxagent on the server side is (thankfully) Version >> 3.5.99.26. >> Please note: the x2goserver resides on a slackware64-current system. But I >> have another reference system (slackware64-15.0) with the exact same >> x2goserver version. >> The reference version works fine and running the same test there works fine >> too, but it does not "halt" at the moment when the problematic halts for >> about 10 seconds. >> >> OK so the log in the problematic system is as follows: >> >> nass@whitestar$ ssh blackstar -X >> Last login: Mon Jan 19 22:37:27 2026 from 192.168.112.145 >> Linux 6.12.63. >> >> nass@blackstar:~$ nxagent :55 >> >> NXAGENT - Version 3.5.99.26 >> >> Copyright (c) 2001, 2011 NoMachine (http://www.nomachine.com) >> Copyright (c) 2008-2014 Oleksandr Shneyder <[email protected]> >> Copyright (c) 2011-2016 Mike Gabriel <[email protected]> >> Copyright (c) 2014-2016 Ulrich Sibiller <[email protected]> >> Copyright (c) 2014-2016 Mihai Moldovan <[email protected]> >> Copyright (c) 2015-2016 Qindel Group (http://www.qindel.com) >> See https://github.com/ArcticaProject/nx-libs for more information. >> >> Info: Agent running with pid '17964'. >> Session: Starting session at 'Mon Jan 19 22:49:53 2026'. >> >> [It seemingly blocks for about 10seconds here. Then it continues...] >> >> Info: Using alpha channel in render extension. >> Info: Not using local device configuration changes. >> Warning: Cannot read keystroke file '/home/nass/.nx/config/keystrokes.cfg'. >> Info: using keystrokes file '/etc/nxagent/keystrokes.cfg' >> Currently known keystrokes: >> close_session : Ctrl+Alt+t >> switch_all_screens : Ctrl+Alt+f >> fullscreen : Ctrl+Shift+Alt+f >> minimize : Ctrl+Alt+m >> defer : Ctrl+Alt+e >> force_synchronization : Ctrl+Alt+j >> resize : Ctrl+Alt+r >> viewport_move_left : Ctrl+Shift+Alt+Left >> viewport_move_left : Ctrl+Shift+Alt+KP_Left >> viewport_move_up : Ctrl+Shift+Alt+Up >> viewport_move_up : Ctrl+Shift+Alt+KP_Up >> viewport_move_right : Ctrl+Shift+Alt+Right >> viewport_move_right : Ctrl+Shift+Alt+KP_Right >> viewport_move_down : Ctrl+Shift+Alt+Down >> viewport_move_down : Ctrl+Shift+Alt+KP_Down >> viewport_scroll_left : Ctrl+Alt+Left >> viewport_scroll_left : Ctrl+Alt+KP_Left >> viewport_scroll_up : Ctrl+Alt+Up >> viewport_scroll_up : Ctrl+Alt+KP_Up >> viewport_scroll_right : Ctrl+Alt+Right >> viewport_scroll_right : Ctrl+Alt+KP_Right >> viewport_scroll_down : Ctrl+Alt+Down >> viewport_scroll_down : Ctrl+Alt+KP_Down >> reread_keystrokes : Ctrl+Alt+k >> autograb : Ctrl+Alt+g >> dump_clipboard : Ctrl+Shift+Alt+c >> error opening security policy file /usr/local/share/nx/SecurityPolicy >> Info: Keycode conversion auto-determined as on >> Session: Session started at 'Mon Jan 19 22:50:04 2026'. >> Info: Screen [0] resized to geometry [1280x965] fullscreen [0]. >> >> At this stage the nxagent window fired up in the server side, has been drawn >> in the client desktop environment as a separate window. >> >> >> >> >> On Mon, Jan 19, 2026 at 9:42 PM Ulrich Sibiller <[email protected]> >> wrote: >>> >>> Hi, >>> >>> You are using nxproxy 3 >>> 5.99.23 which should not be a problem, despite being very old. But maybe >>> you are also using this ancient version on the server. Which IS a problem. >>> Please ensure you use 3.5.99.26 or 27. >>> >>> A quick test to rule out some things: ssh -X ro the server, then run >>> nxagent :55. Do you see an nxagent window? >>> >>> Also, are you sure you have an X desktop running on the server and not >>> wayland? And on the client? >>> >>> Uli >>> >>> >>> >>> Athanasios Silis <[email protected]> schrieb am Mo., 19. Jan. >>> 2026, 19:34: >>>> >>>> Hi all, >>>> I recently installed x2goserver (and x2goclient but this is probably not >>>> relevant in this case) on a fresh slackware-current system. >>>> >>>> Then, using x2goclients from other computers (other slackware64-15.0, >>>> ubuntu20.04 and 24.04 and debian systems) I want to "fetch" a desktop from >>>> this fresh system to one of the other client systems. >>>> >>>> The connection seems to go through normally but I never see a desktop >>>> window poping up. I have tried "xfce" and "fluxbox" (as a custom command) >>>> both of which have been faithfully working in the past and in other >>>> installations. >>>> >>>> I used `x2goclient --debug` to invoke the session and see if there are any >>>> meaningful messages error messages from the client side, but I have not >>>> been able to figure out if there is anything relevant: >>>> >>>> $ x2goclient --debug >>>> qt5ct: using qt5ct plugin >>>> x2go-INFO-1> "Starting X2Go Client 4.1.2.2..." >>>> [...] >>>> x2go-INFO-3> "Started X2Go Client." >>>> [...] >>>> x2go-INFO-8> "Starting connection to server: x.x.x.x:22" >>>> [...] >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:687> User authentication OK. >>>> [...] >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:702> Login Check - OK >>>> x2go-DEBUG-../src/onmainwindow.cpp:2947> SSH connection established. >>>> x2go-DEBUG-../src/onmainwindow.cpp:3374> Continue normal X2Go session >>>> [...] >>>> x2go-DEBUG-../src/sshprocess.cpp:387> Starting tunnel via SshProcess >>>> object 2: "localhost":57842 -> "localhost":58842 >>>> [...] >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2065> Executing remote: >>>> "bash -l -c 'echo \"X2GODATABEGIN:1790db9f-7b15-48ca-9eec-7596bdb1cccf\"; >>>> export PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; >>>> X2GODPI=141 X2GO_XINERAMA=no x2gostartagent 800x600 adsl 16m-jpeg-9 >>>> unix-kde-depth_24 us auto 1 D startfluxbox both; echo >>>> \"X2GODATAEND:1790db9f-7b15-48ca-9eec-7596bdb1cccf\";'" >>>> x2go-DEBUG-../src/onmainwindow.cpp:6142> "Starting NX proxy, command: >>>> nxproxy -S >>>> nx/nx,options=/home/user/.x2go/S-poker-50-1768844727_stDstartfluxbox_dp24/options:50" >>>> [...] >>>> x2go-DEBUG-../src/onmainwindow.cpp:6618> Proxy wrote on stderr: >>>> "\nNXPROXY - Version 3.5.99.23\n\nCopyright (c) 2001, 2011 NoMachine[...] >>>> Info: Connecting to remote host 'localhost:58842'.\n >>>> Info: Connected to remote proxy on FD#5.\n" >>>> >>>> >>>> So it seems ssh connection gets established, login is OK, `nxstartagent` >>>> is executed fine, and `nxproxy` also starts without errors. but then >>>> >>>> >>>> >>>> 2go-DEBUG-../src/sshprocess.cpp:109> New TCP connection. >>>> x2go-DEBUG-../src/sshprocess.cpp:114> New socket: 21 >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1977> Creating new channel. >>>> >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1990> New >>>> channel:0x7f5b580102e0 >>>> >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1994> Forwarding parameters: >>>> from remote ("localhost":57842) to local ("localhost":35710) >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2028> Temporary session port >>>> after config file parse: 57842 >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2032> Temporary session host >>>> after config file parse: localhost >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> [...] >>>> x2go-DEBUG-../src/onmainwindow.cpp:6618> Proxy wrote on stderr: "Info: >>>> Aborting the procedure due to signal '15'.\nSession: Session terminated at >>>> 'Mon Jan 19 19:46:53 2026'.\n" >>>> x2go-DEBUG-../src/onmainwindow.cpp:6475> Deleting Proxy. >>>> x2go-DEBUG-../src/onmainwindow.cpp:6520> Waiting for proxy to exit. >>>> x2go-DEBUG-../src/onmainwindow.cpp:6544> Checking exit status. >>>> x2go-DEBUG-../src/sshprocess.cpp:199> Executing remote command via >>>> SshProcess object 3: "x2gocmdexitmessage >>>> nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/sshprocess.cpp:213> this=SshProcess(0x55f9bbed6c50) >>>> Running masterCon->addChannelConnection(this, >>>> '"475b1d25-5fe0-4e44-abcc-dea30df785f1"', '"bash -l -c 'echo >>>> \"X2GODATABEGIN:475b1d25-5fe0-4e44-abcc-dea30df785f1\"; export >>>> PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; >>>> x2gocmdexitmessage nass-50-1768844727_stDstartfluxbox_dp24; echo \""'); >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1810> Locking SSH channel >>>> connection MUTEX. >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2055> >>>> "ssh_channel_open_forward failed": "No channel request of this type from >>>> server" >>>> >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2187> "ssh_channel_write >>>> failed": "Remote channel is closed" >>>> >>>> then it tries to resume >>>> >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2065> Executing remote: >>>> "bash -l -c 'echo \"X2GODATABEGIN:a6aca35a-a72c-4453-96b1-0a2e1b49dfcb\"; >>>> export PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; >>>> x2goresume-session nass-50-1768844727_stDstartfluxbox_dp24 800x600 adsl >>>> 16m-jpeg-9 us auto 1 both no; echo >>>> \"X2GODATAEND:a6aca35a-a72c-4453-96b1-0a2e1b49dfcb\";'" >>>> >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2071> >>>> "ssh_channel_open_session failed": "Socket error: Success" >>>> >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: >>>> "ssh_channel_open_forward failed."" - No channel request of this type from >>>> server" (2). >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: "ssh_channel_write >>>> failed."" - Remote channel is closed" (2). >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: >>>> "ssh_channel_open_session failed."" - Received SSH_MSG_DISCONNECT: >>>> 2:oclose packet referred to nonexistent channel 0" (3). >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: >>>> "ssh_channel_open_session failed."" - Socket error: Success" (4). >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy window: >>>> X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with >>>> title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" >>>> >>>> and afterwards I get the last 2 messages in an endless loop. No desktop >>>> window pops up. >>>> >>>> >>>> I am also very confused about the >>>> >>>> "ssh_channel_open_session failed": "Socket error: Success" >>>> >>>> >>>> I have not found any information about how to enable debug output in the >>>> server side (only on the client side) and the current messages do not give >>>> me a clear view as to what is wrong. >>>> >>>> Do you have any idea which way I should look next? >>>> >>>> Thank you in advance for your help. >>>> >>>> >>>> _______________________________________________ >>>> x2go-user mailing list -- [email protected] >>>> To unsubscribe send an email to [email protected] >>>> ${mailinglist_url} (substitution broken, will need mailman upgrade) >>>> https://lists.x2go.org/postorius/lists/x2go-user.lists.x2go.org _______________________________________________ x2go-user mailing list -- [email protected] To unsubscribe send an email to [email protected] ${mailinglist_url} (substitution broken, will need mailman upgrade) https://lists.x2go.org/postorius/lists/x2go-user.lists.x2go.org
