[Stuart Cassoff]'s "Communications Endpoints for [Tcl]" 
[http://www.fivetones.net/software/]
gives, among other functionality, [UDP], [IPv6], ...




[["... significant demo of Tcl's extensibility (and Tcl_Channel's as well) ..."]]

[[... only internal mucking is through <tcl.h> ...]]

[[... fully compatible with [socket], [tls], ...]]

[[?Fit for folding back into [core]?]]


"It has been designed so that [Windows] capability would be easy to integrate."
As of May 2005, though, there's no Windows port.