5. How to use a Unix-box as a TCP/IP network provider for the hp, thanks to pppd

5.1 Connection

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:

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 194.149.160.9
ms-dns 194.149.160.1

• /dev/ttySx is the serial port. For HP49G+ via USB, use /dev/ttyUSBx. For HP49G+ via IR, use /dev/ircommx
• 9600 is 9600bps (sig...)
• 10.0.0.1 is the ip of the unix system
• 10.0.0.5 is an arbitrary IP number
• local is because no hardware control is available
• xonxoff should trigger software control, should!
• noccp and novj are not mandatory, but fasten connection
• noauth prevents the Unix box from using CHAP or PAP
• in the same way, silent & persist are here to save time
• proxyarp lets the hp appear on an ethernet network
• lock allows me to switch between pppd and minicom: I kill pppd a dozen times ; then init gives up respawning it, I then can launch minicom, and the lock file will do the rest
• ms-dns lines are there to tell the hp which dns servers to use.

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.

5.2 Bringing interneting to the hp

Check that inetd or xinetd is set up

look at /etc/inetd.conf, and look for lines like:

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.