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    Solved CentOS 7 enabling Telnet

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    telnet centos firewalld troubleshooting ydmp yealink device management
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    • DustinB3403D
      DustinB3403
      last edited by DustinB3403

      OK so still dealing with an issue here (Yealink Device management Platform). I have telnet installed and enabled and running.

      0_1528378610549_putty_2018-06-07_08-23-10.png

      I have firewall-cmd configured and loaded.

      0_1528378573637_putty_2018-06-07_08-25-28.png

      From Windows however I am unable to connect to the server using telnet (yes the client is installed).

      0_1528374535481_cmd_2018-06-07_08-28-48.png

      What else am I missing here?

      1 Reply Last reply Reply Quote 0
      • DustinB3403D
        DustinB3403
        last edited by

        I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

        dbeatoD 1 Reply Last reply Reply Quote 1
        • iroalI
          iroal
          last edited by

          Try to disable SELinux with the command "setenforce 0"

          DustinB3403D 1 Reply Last reply Reply Quote 0
          • DustinB3403D
            DustinB3403 @iroal
            last edited by

            @iroal said in CentOS 7 enabling Telnet:

            Try to disable SELinux with the command "setenforce 0"

            That doesn't correct the issue either.

            1 Reply Last reply Reply Quote 0
            • dbeatoD
              dbeato @DustinB3403
              last edited by

              @dustinb3403 said in CentOS 7 enabling Telnet:

              I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

              What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

              DustinB3403D 1 Reply Last reply Reply Quote 0
              • DustinB3403D
                DustinB3403 @dbeato
                last edited by

                @dbeato said in CentOS 7 enabling Telnet:

                @dustinb3403 said in CentOS 7 enabling Telnet:

                I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

                What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

                How would I do that?

                dbeatoD 2 Replies Last reply Reply Quote 0
                • dbeatoD
                  dbeato @DustinB3403
                  last edited by

                  @dustinb3403 said in CentOS 7 enabling Telnet:

                  @dbeato said in CentOS 7 enabling Telnet:

                  @dustinb3403 said in CentOS 7 enabling Telnet:

                  I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

                  What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

                  How would I do that?

                  Actually, something along this lines might be good:
                  http://sharadchhetri.com/2014/12/08/change-telnet-server-port-number-centos-7-rhel-7/

                  DustinB3403D 1 Reply Last reply Reply Quote 0
                  • DustinB3403D
                    DustinB3403 @dbeato
                    last edited by DustinB3403

                    @dbeato I'm already reading it, but systemd fails to restart the service with

                     systemctl status telnet.socket
● telnet.socket - Telnet Server Activation Socket
   Loaded: loaded (/usr/lib/systemd/system/telnet.socket; enabled; vendor preset: disabled)
   Active: failed (Result: resources) since Thu 2018-06-07 08:35:37 EDT; 14min ago
	 Docs: man:telnetd(8)
   Listen: [::]:9090 (Stream)
 Accepted: 1; Connected: 0

Jun 07 08:37:31 server systemd[1]: Starting Telnet Server Activation Socket.
Jun 07 08:37:51 server systemd[1]: telnet.socket failed to listen on sockets: Permission denied
Jun 07 08:37:51 server systemd[1]: Failed to listen on Telnet Server Activation Socket.
Jun 07 08:37:51 server systemd[1]: Starting Telnet Server Activation Socket.
Jun 07 08:40:15 server systemd[1]: telnet.socket failed to listen on sockets: Permission denied
Jun 07 08:40:15 server systemd[1]: Failed to listen on Telnet Server Activation Socket.
Jun 07 08:40:15 server systemd[1]: Starting Telnet Server Activation Socket.
Jun 07 08:49:31 server systemd[1]: telnet.socket failed to listen on sockets: Permission denied
Jun 07 08:49:31 server systemd[1]: Failed to listen on Telnet Server Activation Socket.
Jun 07 08:49:31 server systemd[1]: Starting Telnet Server Activation Socket.
                    1 Reply Last reply Reply Quote 1
                    • dbeatoD
                      dbeato @DustinB3403
                      last edited by

                      @dustinb3403 said in CentOS 7 enabling Telnet:

                      @dbeato said in CentOS 7 enabling Telnet:

                      @dustinb3403 said in CentOS 7 enabling Telnet:

                      I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

                      What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

                      How would I do that?

                      For the firewall rules this is what I would use:

                      firewall-cmd --zone=public --add-port=9009/tcp --permanent
firewall-cmd --reload
semanage port -a -t telnetd_port_t -p tcp 9099

                      Also are you modifying the following file?
                      /usr/lib/systemd/system/telnet.socket

                      DustinB3403D 1 Reply Last reply Reply Quote 0
                      • DustinB3403D
                        DustinB3403
                        last edited by DustinB3403

                        and the journalctl logs has

                        -- Unit telnet.socket has begun starting up.
Jun 07 08:50:48 server polkitd[713]: Unregistered Authentication Agent for unix-process:3613:205717 (system bus name :1.48, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.
Jun 07 08:57:21 server firewalld[743]: WARNING: ALREADY_ENABLED: 9090:tcp
Jun 07 08:58:16 server polkitd[713]: Registered Authentication Agent for unix-process:3803:250497 (system bus name :1.53 [/usr/bin/pkttyagent --notify-fd 5 --fallback], object path /org/freedesktop/
Jun 07 08:58:16 server polkitd[713]: Unregistered Authentication Agent for unix-process:3803:250497 (system bus name :1.53, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.
Jun 07 08:59:03 server polkitd[713]: Registered Authentication Agent for unix-process:3820:255214 (system bus name :1.54 [/usr/bin/pkttyagent --notify-fd 5 --fallback], object path /org/freedesktop/
Jun 07 08:59:03 server systemd[1]: Reloading.
Jun 07 08:59:04 server polkitd[713]: Unregistered Authentication Agent for unix-process:3820:255214 (system bus name :1.54, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.
Jun 07 08:59:11 server polkitd[713]: Registered Authentication Agent for unix-process:3840:255990 (system bus name :1.55 [/usr/bin/pkttyagent --notify-fd 5 --fallback], object path /org/freedesktop/
Jun 07 08:59:11 server systemd[1]: telnet.socket failed to listen on sockets: Permission denied
Jun 07 08:59:11 server systemd[1]: Failed to listen on Telnet Server Activation Socket.
                        1 Reply Last reply Reply Quote 0
                        • DustinB3403D
                          DustinB3403 @dbeato
                          last edited by

                          @dbeato said in CentOS 7 enabling Telnet:

                          @dustinb3403 said in CentOS 7 enabling Telnet:

                          @dbeato said in CentOS 7 enabling Telnet:

                          @dustinb3403 said in CentOS 7 enabling Telnet:

                          I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

                          What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

                          How would I do that?

                          For the firewall rules this is what I would use:

                          firewall-cmd --zone=public --add-port=9009/tcp --permanent
firewall-cmd --reload
semanage port -a -t telnetd_port_t -p tcp 9099

                          Also are you modifying the following file?
                          /usr/lib/systemd/system/telnet.socket

                          Yes I've done all of this.

                          dbeatoD 1 Reply Last reply Reply Quote 1
                          • dbeatoD
                            dbeato @DustinB3403
                            last edited by

                            @dustinb3403 said in CentOS 7 enabling Telnet:

                            @dbeato said in CentOS 7 enabling Telnet:

                            @dustinb3403 said in CentOS 7 enabling Telnet:

                            @dbeato said in CentOS 7 enabling Telnet:

                            @dustinb3403 said in CentOS 7 enabling Telnet:

                            I just figured it out, it's using the default port. 23 rather than the port I thought I added correctly.

                            What if you create an IPTable forwarding from that 9090 port to the internal port 23? Does that work?

                            How would I do that?

                            For the firewall rules this is what I would use:

                            firewall-cmd --zone=public --add-port=9009/tcp --permanent
firewall-cmd --reload
semanage port -a -t telnetd_port_t -p tcp 9099

                            Also are you modifying the following file?
                            /usr/lib/systemd/system/telnet.socket

                            Yes I've done all of this.

                            Interesting, I am not sure then.

                            DustinB3403D 1 Reply Last reply Reply Quote 0
                            • DustinB3403D
                              DustinB3403 @dbeato
                              last edited by

                              @dbeato I've even modified the predefined service at /usr/lib/firewalld/services/telnet.xml to use port 9090 and the service still fails to load.

                              1 Reply Last reply Reply Quote 1
                              • DustinB3403D
                                DustinB3403
                                last edited by

                                And I got the port forwarding to work.

                                firewall-cmd --zone=public --add-forward-port=port=9090:proto=tcp:toport=23

                                I can now telnet to my server on port 9090 (which forward to 23).

                                dbeatoD 1 Reply Last reply Reply Quote 2
                                • dbeatoD
                                  dbeato @DustinB3403
                                  last edited by

                                  @dustinb3403 said in CentOS 7 enabling Telnet:

                                  And I got the port forwarding to work.

                                  firewall-cmd --zone=public --add-forward-port=port=9090:proto=tcp:toport=23

                                  I can now telnet to my server on port 9090 (which forward to 23).

                                  Nice!

                                  1 Reply Last reply Reply Quote 0
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