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IP Communication Question

JeffJeff Junior MemberPosts: 374
I'm experiencing a problem with IP Communication with some projectors I have. I'm fairly new to IP Comm, and I can't tell if this is a legitimate issue or its just something you have to deal with on certain models.

I'm trying to connect to InFocus LP820 projectors which are on our network and have static IP addresses. The manual (pdf) says nothing about it at all, and the command protocol (pdf) is equally useless on the matter. If I telnet into them, I can send the same commands I would normally do via RS232 and get the correct responses. However, after about 30 seconds, I get disconnected. This happens EVERY time, on several different projectors. Its almost as if there's a max connection time limit that is kicking in or something. I tried using AMX to connect to it, and if I connect via port 23, I get the exact same results. I tried connecting on 24 (which is what I control my Polycoms, the only other IP device I've ever used, with), and it wouldn't even connect.

So I have a few questions

Is it not unusual to not be able to connect long term to a device?
If so, how do people control devices like this? Issue IP Open commands before every command/query is sent out? That'll be tricky, because I want to constantly poll this projector.
Or should I just be using a different port to connect to this?

Any help will be appreciated, I can't tell how much of this is a poorly designed projector and how much is an underexperienced programmer



  • Marc ScheibeinMarc Scheibein Junior Member Posts: 669
    There are several IP controlled devices which will disconnect after a given time if no data is sent. In this case, ecverytime I want to send a new control string, I first have to check if the IP connection is still established, and if not, I first have to establish it before sending.

    Example of IP control:
    And 2 examples from me I send my customers.
  • Chip MoodyChip Moody Junior Member Posts: 727
    Jeff, standard telnet connections are done on port 23. Polycom gives you port 24 for control because it doesn't spit out the very chatty debuging information that the standard telnet port does.

    For your projectors, you'll want your Netlinx code to talk over port 23. To avoid having the connection timeout, you might throw a lamp hour query (or something similar) every 10 seconds to keep the connection alive.

    Otherwise, be sure to use the ONLINE and OFFLINE handlers to keep track of whether your connection is alive or not. (Try to avoid sending data out if the connection is dead)

    Also look into the values returned in the ONERR handler for the device's DATA_EVENT - they can be helpful in figuring out/tracking when connections drop.

    - Chip
  • JeffJeff Junior Member Posts: 374
    ok, thanks a bunch guys.

    Further testing after reading your responses reveals that you're right, sending it a regular command keeps it from dropping out, it only drops out after 30 seconds of inactivity. Since I'll be polling every few seconds to find out a few things (power, input, etc), it shouldn't ever drop out. I always track online/offline in the event handlers, so I should be able to check and fix things if it drops offline, and that should take care of things.

    Thanks a bunch guys.

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