PLIP Problem

DISCUSSION Yann COLLETTE 1 participant 1 message May 15, 2003

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Yann COLLETTE

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2003-05-15 07:37 UTC #0 lore raw

Hello,

Sorry for the late answer.
Thanks for the tcpdump thing. I've tried it and I saw nothing on the link.
So I verified that the parallel port was correctly configured and ... it was (I was able to print things on my printer).
No error/warning messages about plip.
So, I returned back to my computer shop and looked at what precisely had I bought:

A SERIAL null-modem ?

I thought null-modem was only dedicated to parallel port ?
So, I bought a PARALLEL null-modem and now it works fine (with kernel 2.4.19).

Your sincerely,

Yann COLLETTE

Quoted 103 lines · Riley Williams

Hi Yann.
Quoted 3 lines
I'm trying to connect a laptop to a my home computer using a PLIP connection. On both computers, I've a Linux Mandrake 9.0 with a kernel 2.4.20.
I've never specifically used PLIP but there are some points to be cleared up in your email...
Quoted 2 lines
In /etc/hosts, I have pc.home.org 198.168.0.1 and laptop.home.org 198.168.0.2
Do you mean 192.168.0.1 and 192.168.0.2 respectively? The addresses you quote are valid across the Internet rather than being reserved for local LAN use.
Quoted 8 lines
For /etc/hosts.allow and /etc/hosts.deny, I've followed the PLIP-HOWTO advices. I've configured the parport_pc module (for both pc):
insmod parport_pc io=0x378 irq=7
The kernel messages are fine with this configuration. Then I load the PLIP module (insmod plip).
That looks fine so far...
Quoted 9 lines
On the laptop, I do:
ifconfig plip0 laptop.home.org pointopoint pc.home.org \
       netmask 255.255.255.255 up
route add -host pc.home.org dev plip0
And on my home computer I do:
ifconfig plip0 pc.home.org pointopoint laptop.home.org netmask >
255.255.255.255 up
Quoted 1 line
route add -host laptop.home.org dev plip0
I seem to remember that pointopoint implies netmask 255.255.255.255 in which case the latter could be omitted.
Quoted 2 lines
On the laptop, when I ping the pc, nothing happens and on the pc, when I ping the laptop, nothing happens too.
Are your systems set up to respond to ping's ?
As a better test of connectivity, run tcpdump -i plip0 on one end, then run the ping on the other. That will show you whether there's any traffic going over the link. Swap them over and you'll check the other direction as well. Use CTRL-C to stop tcpdump.
Quoted 4 lines
I don't know where I am wrong:
- Maybe my parport is not really bidirectional on my laptop (how can I know if a parport can communicate ?)
The above tcpdump test will show that.
Quoted 4 lines
- Maybe there's a problem with the way I configure the PLIP module (I don't known how to dive into the kernel sources to extract information about how to configure a module. There are no information about the PLIP module in the kernel documentation).
Other things to check:
* What type of parallel port do you have?
This is normally configured in the BIOS setup, from the following options - the higher up this list, the better.
          EPP 1.9
          EPP 1.7
          EPP/ECP
          ECP/EPP
          ECP
          Normal
* Is your cable wired correctly? Depending on the type of parallel port, you need one of two different sets of wiring - either the "Standard LapLink" or the "Wide LapLink" cable.
The tcpdump test above will answer this question. Simply put, if there is traffic passing both ways then the cable is correct.
* Do you have a firewall set up on either system? If so, disable it and see if that fixes the problem.
Personally, I was stung by the last item recently, and that's with a standard Ethernet link where there's less to go wrong to start with.
Best wishes from Riley.
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