On Thu, Aug 23, 2007 at 03:37:00PM +0200, Fili Wiese wrote: > I'm having trouble setting up a serial connection between two servers > using a null modem cable. > This link is needed as a redundant connection for Heartbeat. > Both machines are indentical (both hardware and software). > > In my humble view, everything seems to be set up perfectly. > However, an echo/cat test simply doesn't work: > > server1: echo test >/dev/ttyS0 > server2: cat </dev/ttyS0 > (no output) > > I'm really at a loss :S > Does anybody have a clue where to look next? > > Maybe the (brand-new) null-modem cable is not wired properly but how do > I find that out? >
Since cat doesn't set up the port for use, it won't work. I have yet to find a ready-made null-modem cable that is actually wired correctly for use by UNIX. How it should be wired can be found in several places accessible as packages on Debian. Serial-HOWTO Modem-HOWTO, both in the doc-linux-HOWTO package Hardware book, available in the hwb package. Also, in book form: Unix System Administration Handbook. Nemeth, Evi, et.al. The actual wireing of the cable can be verified with an ohm-meter if you have both ends of the cable in your hand, or by putting a wrap plug on one end. The functioning of the link can be verified with minicom. If you put a wrap plug on one end, and the other end on one of the servers, you can use minicom and talk to yourself. The signal goes down the wire, through the wrap plug and back you your box. Then you can run minicom at both ends an talk. Setting up ppp or something over the wire is a possibility but it won't provide any further details if you don't need ppp. If you _do_ need ppp, then the PPP-HOWTO will tell you how to setup a link. Its really quite easy. Basically you set up mgetty on one box and have ppp on the other box access it. Since there's no modem, there are no dialing strings. Doug. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
