TCP/IP over Infra-red on the Empeg

© Amit Singh. All Rights Reserved. Written in 2001

When you think about it, there are so many strings attached to infra-red data transfer. It must be short range, must be line-of-sight, and so on. However, there are numerous benefits as well: it is reasonably high speed (up to 4 Mbps for what is called fast infra-red), it is cordless, it is not exactly limited to line of sight, there is a plethora of devices that support IR out there, and so on. Oh, and it is cool in general. With an increasing number of computers (particularly laptops) including infra-red ports today, support for IrDA has been gaining momentum. In particular, open source IrDA support for Linux is eminently usable already. Following is a diagram (click here for a bigger picture) displaying the IrDA stack.

IRDA Stack

Making two Linuces talk TCP/IP over IR

Linux 1: Sony VAIO

I have a Sony VAIO PCG-Z505 JE laptop, on which IrDA works well. The IrDA specific contents of my /etc/modules.conf are given below.

# Sony VAIO PCG-Z505 JE (Linux 2.4.9, irda-utils-0.9.14) # pre-install nsc-ircc setserial /dev/ttyS2 port 0 irq0 alias irda0 nsc-ircc options nsc-ircc io=0x3e8 dma=0 irq=10 dongle_id=0x09 alias tty-ldisc-11 irtty alias char-major-161 ircomm-tty alias char-major-10-187 irnet

Linux 2: The Empeg

I am running the Debian potato distribution on the Empeg, as described in this HOWTO. In order to use IrDA as we are going to, the following are required on the Empeg:

It is easiest to use SIR to get started with IrDA (which I reckon is the only way that will work on the Empeg because of its IR hardware). We shall use PPP over SIR to get TCP/IP working. Communication speed will be limited to 115200 bps. The following steps should allow you to get a minimal connection working, which you can tailor to suit your needs thereafter:

Please note that IrComm is not the only way to connect the Empeg to an IR-enabled computer, but it is the simplest. IrLAN in ad-hoc mode might be another option.