The kernel must be compiled with async ppp support (either within the kernel or as a loadable module), and the pppd package must be installed
Linux users must apply a patch so as to get xon/xoff working: see http://youpibouh.thefreecat.org/info/prog/4xinet.html
then, you'll have to launch pppd on the connected serial port: for instance, in my /etc/inittab file, there's the line:
and in /etc/ppp/peers, there's the file hp containing:
hp:2345:respawn:/usr/sbin/pppd nodetach call hp &>/dev/null
/dev/ttyS0 9600 10.0.0.1:10.0.0.5 local xonxoff noccp novj noauth silent persist proxyarp lock ms-dns 184.108.40.206 ms-dns 220.127.116.11
Make sure that there is no lcp-echo-interval or lcp-echo-failure in /etc/ppp/options (else the connection would keep breaking...)
type init q to ask init to reread inittab, and voilà!
You can now connect to you Unix box at any time.
Check that inetd or xinetd is set up
look at /etc/inetd.conf, and look for lines like:
If a # precedes them, erase it. If they don't exist, type them.
time dgram udp wait root internal tftp dgram udp wait nobody /usr/sbin/tcpd /usr/sbin/in.tftpd /home/tftp
Then try something like /etc/init.d/netbase restart, or /etc/rc.d/init.d/inetd restart, or any mixture of both :) If inetd isn't automatically started at bootup, you should ask it to be.
Hp can now ask for the time by using NETTIME, or for a file located in /home/tftp by using TFTP.
That's not much, but it's up to you to write your own interneting programs, using usinagaz! (see examples in bin)
Well, you may also use your Unix box as a gateway to internet for your hp, thanks to forwarding and masquerading. Please look at the appropriate howtos.