If you are using an Indy workstation retrieve audior, audioc, faucet, hose, talkto, and listento from the Sources and Executables page and place them in an appropriate directory.
If you must recompile audior.c or audiop.c, use the gcc command as follows:
gcc audior.c -laudio -lm -o audior (and similarly for audiop)
If you need to compile your own faucet and hose, retrieve and untar netpipes2.1.tar from the Sources and Executables page. Then run make faucet and make hose.
Make the necessary modifications to the talkto and listento shell scripts. You will need to change the directories to reflect those that you are using. You only need to change the port from 2010 to a different number if that port is already in use.
Run talkto on your machine and have the other person run it on their machine.
Once the one person has executed talkto, run listento as follows:
listento machinename (where machine name is an IP address or an actual machine name)
Use kill Process# to kill each process when you are done.
You only need to run talkto once to serve a conference call. You will have to run multiple instances of listento to listen to each person.