PuTTY is a free implementation of telnet, ssh and terminal emulation by Simon Tatham. It seems to be the preferred way to play NetHack on a public server on Windows, as it is much more versatile and standards-compliant than Microsoft's telnet.exe that comes with Windows.
PuTTY can be downloaded from PuTTY homepage
To make IBMgraphics work with PuTTY, you need to set Window/Translation/Character Set to CP437
To make PuTTY looks exactly like the Windows terminal window, set Windows/Appearance/Font to Terminal
Make sure "auto-wrap mode" is switched off or you terminal might get spammed with text artifacts.
When connecting to server using Dgamelaunch, you may become disconnected if you accidentaly resize Putty window to have different width or height in onscreen characters. To prevent this from happening choose between Change the size of the font (having larger letters is eyes friendly and putting this to fullscreen looks cool) and Forbid resizing completely in Window settings. You can also set the starting window size here.
(from Putty documentation)
PuTTY has a special mode for playing NetHack. You can enable it by selecting ‘NetHack’ in the ‘Initial state of numeric keypad’ control.
In this mode, the numeric keypad keys 1-9 generate the NetHack movement commands (hjklyubn). The 5 key generates the . command (do nothing).
In addition, pressing Shift or Ctrl with the keypad keys generate the Shift- or Ctrl-keys you would expect (e.g. keypad-7 generates ‘y’, so Shift-keypad-7 generates ‘Y’ and Ctrl-keypad-7 generates Ctrl-Y); these commands tell NetHack to keep moving you in the same direction until you encounter something interesting.
For some reason, this feature only works properly when Num Lock is on. We don't know why.