dev@apertus-dev:~$ ssh -v -p 2224 -X andrej@www.apertus.org 'xcalc'
OpenSSH_7.7p1 Ubuntu-4ubuntu0.2, OpenSSL 1.0.2n  7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to www.apertus.org [213.145.235.244] port 2224.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_rsa-cert type -1
debug1: identity file /home/dev/.ssh/id_dsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_ed25519-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_xmss type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.7p1 Ubuntu-4ubuntu0.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.6
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.6 pat OpenSSH* compat 0x04000000
debug1: Authenticating to www.apertus.org:2224 as 'andrej'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:knxANGoPeUGWyv73eZWSC755Ry0x6CZn53MwVIQcwVs
debug1: Host '[www.apertus.org]:2224' is known and matches the ECDSA host key.
debug1: Found key in /home/dev/.ssh/known_hosts:9
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:vyF3+yMIIidqPDn2nJKlKzoSBd4FCgjV/SwadMDeNkw /home/dev/.ssh/id_dsa
debug1: Server accepts key: pkalg rsa-sha2-512 blen 277
debug1: Authentication succeeded (publickey).
Authenticated to www.apertus.org ([213.145.235.244]:2224).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: exec
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Sending environment.
debug1: Sending env LC_MEASUREMENT = de_DE.UTF-8
debug1: Sending env LC_PAPER = de_DE.UTF-8
debug1: Sending env LC_MONETARY = de_DE.UTF-8
debug1: Sending env LANG = en_GB.UTF-8
debug1: Sending env LC_NAME = de_DE.UTF-8
debug1: Sending env LC_ADDRESS = de_DE.UTF-8
debug1: Sending env LC_NUMERIC = de_DE.UTF-8
debug1: Sending env LC_TELEPHONE = de_DE.UTF-8
debug1: Sending env LC_IDENTIFICATION = de_DE.UTF-8
debug1: Sending env LC_TIME = de_DE.UTF-8
debug1: Sending command: xcalc
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 45508
debug1: channel 1: new [x11]
debug1: confirm x11
X11 connection rejected because of wrong authentication.
debug1: channel 1: free: x11, nchannels 2
Error: Can't open display: localhost:11.0
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
debug1: channel 0: free: client-session, nchannels 1
Transferred: sent 3380, received 3008 bytes, in 0.6 seconds
Bytes per second: sent 5752.0, received 5119.0
debug1: Exit status 1