using tmate.io for ssh tunnel

[Simplenuity]

I'm not sure if my endeavor is even possible?

My idea is to use tmate.io for creating an SSH tunnel as described here:
https://github.com/Genymobile/scrcpy/blob/master/doc/tunnels.md
Not only as a great solution for ad-hoc remote support/management without router modification or having to utilize a full blown remote Desktop session. But also because the issue I have with the latter.

My steps:

• remote system

  • tmate session started -> provides necessary string ssh <string1>@<string2>.tmate.io

• local system

  • normal ssh access to remote system works:
    ssh <string1>@<string2>.tmate.io

  • creating a tunnel fails:

   ssh -CN -L5038:localhost:5037 -L27183:localhost:27183 <string1>@<string2>.tmate.io
  

  output:

   bind: Cannot assign requested address
   bind: Cannot assign requested address
   Connection to <string2>.tmate.io closed by remote host.
  

  for completeness, also this fails:

   ssh -CN -L5038:localhost:5037 -R27183:localhost:27183  <string1>@<string2>.tmate.io
  

  output:

   bind: Cannot assign requested address
   Warning: remote port forwarding failed for listen port 27183
   Connection to <string2>.tmate.io closed by remote host.
  

Any help would be appreciated.