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"

Do you have any idea which way I should look next?

Thank you in advance for your help.