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COM ports and IP address question

By MCThielges
Jun 21, 2016
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  1. My technical computer understanding is mediocre and I was hoping for some education (I've tried figuring this out all day). I am using software that controls an external device connected via USB. I see the device connected to COM3. Upon opening the software, I am prompted to connect to the device with a dialog box that asks for input of the port number and IP address for the device. Everything I have tried gives a connection error. From my (bad) understanding, doesn't the IP address remark my computer, and COM3 the particular port to connect to that address? Or does the device connected via a serial port have its own IP address? I run ifconfig and only see the computer IP and that of another, unrelated device. I assume that the port is "COM3", or 3. I have tried various things for both the port and IP address, including the computer's and 0x3E8 for IP address, "3" and all port numbers listed by ipconfig. I realize that without specifics of the software, help might be limited, but thought I'd reach out to see if anyone might help me understand the problem. Thanks.
  2. Cycloid Torus

    Cycloid Torus Stone age computing. Posts: 3,618   +987

    Hmm. Typically a device connected by USB would be identified and configured with drivers by the operating system. Wireless printers may use a wireless network connection - by obtaining an IP from the router. Several devices could request and each obtain individual IP. You seem to have something quite out of the ordinary. USB is an outgrowth of serial port tech (COM1, etc) and has almost totally replaced it. Unless this is very old equipment, I am surprised it is looking for COM3 (RS232).

    It would be useful to know about your system, its operating system and the device. Model numbers help hugely.
  3. MCThielges

    MCThielges TS Rookie Topic Starter

    I appreciate the reply. New device, simple communication needs I presume. Very specialized - the software controls fairly simple triggering timing for a laser system (I'm better with optics than electronics). I wouldn't ask, or think it would be ultimately fruitful, to bother you with model details - part of the difficulty is dealing with the big laser company that doesn't like to provide helpful details that enable one to actually troubleshoot an issue. Their asking for the IP address is what really confuses me. I have another laser system connected via ethernet, so perhaps they gave me software that assumed the other one was the same? You reassure me that I'm not neglecting something obvious ;) I think I'm going to have to harass the source.
  4. Cycloid Torus

    Cycloid Torus Stone age computing. Posts: 3,618   +987

    OK, begins to make more sense. You have a scientific instrument (laser) which you are trying to attach and control from a PC or equivalent. The hardware layer is defined by the physical properties of the device - it uses USB. The control software appears to be using an archaic version of USB - RS232. There is a memory address for COM3 in your PC (at 0x3E8 ) and it can be enabled in BIOS.

    There is probably a way to use that with some kind of utility and hardware combination which converts RS232 to USB, but I do not know it. There is a lot of free stuff for laser light shows and that enthusiasts group might offer more support.

    Updated software which uses USB at both ends would be the easiest answer - or there may be a patch for that in your package.

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