Remote access to UNIX
Remote access servers are listed here.
PuTTY is a free and open source terminal emulator application which can act as a client for the SSH, Telnet, rlogin, and raw TCP computing protocols and as a serial console client. The name "PuTTY" has no definitive meaning, though 'tty' is the name for a terminal in the Unix tradition, usually held to be short for teletype.
NX is no longer being supported. Please see Xrdp below.
For more suggestions see: here
Xrdp is based on the work of FreeRDP and rdesktop, xrdp uses the remote desktop protocol to present a GUI to the user.