Dialup networking requires both computers to have ppp enabled in the kernel and installed. One of the computers must dial the phone and the other must answer. Once the phone is answered ppp will take care of the connection and the computer that would be refered to as the server should be setup to share the internet connection with the computer that you would call the client. You can also do a shell login over the connection, use sftp, ssh, scp, http, or anything else you need to use.
A getty program will answer the phone and start ppp on the server. For the client you can use command line, ppp scripts, or a gui like kppp if you want.
It is too involved to simply write it all down here, try this and let us know if you have any problems or questions.
I have been using mgetty for years without a problem.
Maybe this will help, here is my /etc/ppp/options file on the server
Here is my entry in /etc/inittab to run mgetty for answering the phone..
S0:2345:respawn:/sbin/mgetty -s 57600 -x 3 ttyS0
Here is my /etc/mgetty+sendfax/login.conf file entry...
/AutoPPP/ - a_ppp /usr/sbin/pppd auth -chap +pap login asyncmap 0 192.168.1.101:192.168.1.201
I also setup my serial port in rc.local like this..
setserial /dev/ttyS0 spd_hi
Using mgetty my server will also accept incoming faxes. It auto detects the connection and either receives a fax or logs in a user. It also emails out your incoming faxes.