From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mariano Moreyra" Subject: RE: tcpdump equivalent for the serial port Date: Fri, 12 Sep 2003 11:08:59 -0300 Sender: linux-c-programming-owner@vger.kernel.org Message-ID: <000801c37937$6b42adc0$0b04a8c0@aca.org.ar> References: <3F61D1CE.7080404@abcpages.com> Reply-To: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <3F61D1CE.7080404@abcpages.com> List-Id: Content-Type: text/plain; charset="us-ascii" To: 'Nicolae Mihalache' , mariano_moreyra@aca.org.ar, linux-c-programming@vger.kernel.org I'm using that cable between a PC and a Fiscal Printer, but it's a RS232 link... We didn't have any problem with signal variations. But I understand that with an RS422 link you could have more problems. Wish I could help you, but I don't know how to write a software to do this kind of sniffing. -----Mensaje original----- De: Nicolae Mihalache [mailto:mache@abcpages.com] Enviado el: Viernes, 12 de Septiembre de 2003 11:02 Para: mariano_moreyra@aca.org.ar; linux-c-programming@vger.kernel.org Asunto: Re: tcpdump equivalent for the serial port Mariano Moreyra wrote: >Hi Nicolae, > Hi Mariano! >I think that what you want to do is not posible just with a software. >You have to build a special cable to do that (somebody tell me if I'm wrong, >or if knows another option) >In my job we have one of those cables because we needed to see what was >going on between two applications that talk to each other via serial port. >The bad thing is that you need a third computer that would be the sniffer. > The problem is that opening the cable and connecting it to a third port may introduce some variations in the signals going over the serial cable. This is something that I want to avoid as much as possible. The other end of the serial cable is not another computer but a device that is itself the subject of development and test so it can not be assumed as working nor it can be developed with a non-nominal serial cable connected to it. Even worse, my serial link is not RS232 but RS422 which has a higher speed and it's more difficult to have break-out capability without interferences. This is why I'm looking for a software solution, i.e. something that communicates with the serial driver and gets all the messages that pass through it. Nicolae