3.13. Linux to Linux Connection

3.13.1. Connection Methods

There should be four ways to get two Linux machines connected via Linux/IrDA.

• Dag Brattli wrote about the IrOBEX support: "The awakened reader may wonder what prevents the beaming of files from Linux to Linux? Well, nothing!! (but I haven't tried that yet). This means that we now have a "simple" way of beaming files between Linux laptops. I think that this may be the "killer app" we all have been waiting for!" Try to "load_misc irobex at both ends, and then try irobex_app get on one of the machines and irobex_app put <file> on the other.".

• Via Linux/IrDA network connection. But currently the IrLAN protocol is no longer maintained by the Linux/IrDA core team.

• With IrCOMM support, in other words over a serial line, which could mean minicom, pppd, etc. If you want just now to use IrCOMM between Linux boxes, please add this line to /etc/conf.modules of _one_ box:

  # set ircomm protocol engine to client-only mode options ircomm ircomm_cs=1

  Note: Don't add it to both boxes, or they cannot accept incoming connection each other! But since 2.2.7 there's no need to add options ircomm ircomm_cs=1 to /etc/conf.modules anymore. Please remove it if you are using it.

• IrNET

3.13.2. Compression

Please note this feature is still quite experimental! Dag Brattli wrote: "Just wanted you to know I have just added COMPRESSION support to IrLAP! As you may know, this is _not_ part of the IrDA(TM) standard, but Linux can now negotiate with its peer and check if it has the same compression capabilities). So obviously if you are talking to Win95, Palm III or whatever, you will _not_ get compression!!! This is something which is exclusive for Linux as far as I know! The IrDA(TM) standard says that devices should ignore unknown field in the negotiation header, so we are still "compatible" with IrDA(TM) (have just borrowed an unused header value).

If you want to try using the compression code (Linux <-> Linux) you will have to insert the irda_deflate module some time before you actually make the connection. I do it before irattach.

The compression standard I have added is the deflate format used by the zlib library which is described by RFCs (Request for Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).

The compression interface is similar to PPP, so you can add as many different compressors as you want. Currently there is only support for GZIP, but BSD compression will be added later. ... Have just tested GZIP compression at 4Mbps. It was a really bad idea! Compressing the frames takes so much time that the performance is actually worse than when not using compression at all. The conclusion is that compression should only be used for SIR speeds, ..."