It does not work with the tellvox program, but you could use the TCP plugin to send messages to VC instead of using UDP. In the TCP plugin settings, select "enable simple web server" and set the port to use. Port 80 is fine but you might already have something else using that port. Save options and restart VC to restart the server with the new port.
Commands can be sent using the URL, the same way that we send commands to Halx, using http get.
Example, if the TCP plugin is configured to use port 8082 you can send a message with the following URL:
http://127.0.0.1:8082/api/tts.speak&&hello%20there
or in general
http://ip.address.of.vc:port/api/action.name&¶m1&¶m2&&etc