I have installed a telnet server, now I want to connect to it without port forwarding - is this possible?
Some programs working without port forwarding like utorrent for example.
You will need to set up port forwarding to connect to your telnet server from outside your network (from the Internet).
Programs such as uTorrent use a special technology, called uPnP, which the telnet server does not support.
As an additional note, you probably should not use telnet as it is insecure. SSH has replaced telnet in that respect. There are plenty of free SSH servers for Windows, all you have to do is Google for them.