[Gllug] USB-over-CAT5

[Matthew King]

I have two computers at opposite ends of the house which need a
serial-line connection between them. There is currently a length of CAT5
cable between them and pulling up floorboards does not sound pleasant.

I have tried an external ADSL modem (so that the router can be moved
closer to the network hub (and therefore within range of a regular
serial cable) but external ADSL modems all appear to be pretty
crap. D-Link's DSL-320T, for example, categorically does not (according
to their technical support) allow me to use more than one IP of my IP
range.

The next best solution, therefore, is to use the existing cable to
transmit serial data. Lots of very expensive devices are available to
coerce USB or RS232 onto IP, however I am considering a more
basic configuration on which I ask GLLUG's advice:

CAT5 cable has 8 wires. Ethernet uses 4. USB uses 4. 4 plus 4 equals
8. Perhaps you can see where I'm going?

The four wires which Ethernet doesn't use I'd like to remove from the
RJ45 connector at each end. At one end plug them into the USB socket in
the router. At the other connect a USB-to-RS232 converter into which I
can plug a short null-modem serial cable.

Because I can't resist the temptation to pointlessly draw it:

\
 \
R |
O |-USBA-\                         /-USBB-<RS232 device>-...
U |       \====} CAT-5 Cable {====/
T |       /====}             {====\
E |-RJ45-/                         \-RJ45-<SWITCH>-...
R |
 /
/

The only drawback I can see is that as the two connections are sharing
one cable there is likely to be interference between the two however, as
the serial port will be barely used (it is only for recovery of the main
server on the LAN), I hope this will be negligible.

Is this a good idea or am I just going to end up breaking things badly?

Matthew

Actually another problem I've just thought of - getting just 4 wires
into an RJ45 plug in the right order is going to be incredibly painful.

-- 
I must take issue with the term "a mere child", for it has been my
invariable experience that the company of a mere child is infinitely
preferable to that of a mere adult.
                                           --  Fran Lebowitz

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