Stuart Cassoff's "Communications Endpoints for Tcl" [L1 ] gives, among other functionality, UDP, IPv6, ...
What: ceptcl
Where: http://www.fivetones.net/software/
Description: Provides a variety of new socket types and greater
control over socket options. Includes
Domains : local (AF_UNIX), inet4 (IPV4), inet6 (IPV6)
Types : tcp, udp, raw
Options : boradcast, multicast, etc.
ceptcl is designed to be backward compatible with
existing Tcl socket apps. It is intended that
all you need to do to use ceptcl is to require the
package and change the invocation of 'socket' to 'cep'.
Tested on OpenBSD, MacOSX, NetBSD, Linux.
Currently at version 0.3 .
Updated: 04/2005
Contact: See web site
["... 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.