The HyperCard MacTCP Toolkit version 1.0 is available from APDA and
provides the functionality that you want. Here is the description from the
APDAlog:
This toolkit contains XCMDs and source code for using HyperCard
with MacTCP. Included is a sample stack for reading "netnews"
and a documentation stack. MacTCP is software that allows
developers to create Macintosh applications for networking
environments that use TCP/IP protocols, a widely used standard
for networking heterogeneous systems.
We haven't heard of a stack that supports the Telnet protocol.
There is an FTP client stack, called HyperFTP, written by Douglas Hornig of
Cornell University. The latest version is available for anonymous FTP
download at elroy.cit.cornell.edu (128.253.232.14).