while working at this project I wrote a convenient library that allow to actually login and send commands to a generic telnet server.
The anwsers received from the server is printed by default on serial, but you can can change this with a little hack at the "print" method of the client itself.
You can find it here.
I think the included example is self-explanatory about its usage but for any questions or suggestions you can write me here.
At the moment I tested it using a raspberry pi as server on my home network...if someone want to test it on different server are welcome!
Hope it can be useful!
I recommend you to consider moving the library to the root of the repository. The reason is this will allow installation by downloading the .zip file of the repository and then using the popular "Add .ZIP Library" installation method. This will also allow the possibility for you to add the library to the Arduino Library Manager index to offer an even easier option for installation and updates.
The only downside to this is that the library folder won't match the primary header file name. This could lead to the Arduino IDE picking the wrong file to include if there are multiple libraries that contain the same file name but I don't think that likely in this case. The other downside is that some ancient IDE versions don't support library folder names with a hyphen in them but you have to draw the line on backwards compatibility somewhere.
ok, just did it...thank you for your hint!