Lynx Software, Networking and Firewalls

This article provides a brief overview of some of the possible networking and firewall issues that could be encountered when initially setting up Uniwell Lynx (FTP) or SharpLynx (MWS) communication across a local area network.

Please note:  Because every computer varies in configuration and stability, and the various anti-virus and firewall programs have different settings, this article cannot provide a definitive solution to all networking or communication problems.  A local computer / networking technician may be needed to assist in troubleshooting difficult communication problems.

The Basics

While some networking issues can be quite technical, it must be emphasised that the majority of communication problems are simply resolved by checking the communication fundamentals:

  • Check cabling – make sure that the network switch ports from both computer and POS terminal have connectivity lights
  • Double check that the computer and POS terminal have valid IP Addresses on the same subnet, and that those IP Addresses do not conflict with other devices on the network
  • Use the ‘Ping’ function from the command prompt to check basic connectivity – if you can’t ping the device, there is a reasonable chance that these basic settings are incorrect (remember that the ‘ping’ command uses the ICMP network protocol, which is usually allowed through firewalls automatically)
  • Make sure that the POS terminal is correctly set for communication – eg. Uniwell AX/HX terminals require Username and Password settings for FTP communication, and Sharp has MWS Config settings (PGM2) that indicate the IP Address of the communicating computer


If you can ping the POS terminal from the computer and believe that the POS terminal is configured correctly, but communication from your Lynx Software still won’t work, the next thing to check are your Firewall settings:

  • If you are using the Windows firewall, typically you simply need to add ‘incoming exceptions’ for Uniwell Lynx (ULE.exe [ELA License] or ULU.exe [USB license] and Unicom.exe) or SharpLynx (SLE.exe or SLU.exe) – go to Control Panel, find the Advanced firewall settings, and create a new ‘Inbound Rule’
  • Some firewall programs block specific networking ports – so you may need to add an exception to allow a specific port number (eg. FTP = port 21, MWS = port 49152) to come through the firewall
  • Bear in mind that if you change TCP/UDP port settings being used by Lynx Software, the corresponding setting must be changed in the POS terminal – however this is not recommended unless you understand what you are doing, and don’t have other software programs that could conflict with the new setting
  • You can typically disable a firewall temporarily to test communication without the firewall interfering.  But remember – the end-user understandably will require the firewall to be operational under normal circumstances – so even if you disable the firewall and communication works, you’ll need to figure out how to get the communication operational with the firewall enabled again
  • Check that you don’t have multiple firewalls operating – its not unheard of to find a computer that has the Windows Firewall functioning, as well as an additional 3rd party firewall installed that is causing its own set of problems
  • Once you have the firewall configured to allow communication, its a good idea to restart the computer and re-test communication again.  This will give you a good indication that communication will operate under normal, default circumstances

Other Troubleshooting Ideas

  • We have seen examples of viruses, rogue software and corrupted Windows installations causing communication to fail.  Its the end-users responsibility to have these sorts of issues fixed
  • There have been rare instances in the past where network communication to a POS terminal has been hindered by the type of network hub being used.  Lynx Software recommends the use of a network switch, rather than a hub. Again, if this seems to be the problem, isolate the issue by connecting the computer and POS terminal(s) via a known-working network switch and then test communication
  • Recent changes to electrical or network wiring may have created an interference problem.  Admittedly, this is another rare occurrence, but if you’ve had recent electrical work done, or recent storm activity or power brown-outs, there could be issues with your cabling, faulty wiring sockets, etc.  We would suggest isolating the cabling (use a long patch lead between the POS Terminal or computer and the network switch) if you have any suspicion that existing cabling may be causing the problem
  • If you have a second computer (eg. the reseller has a laptop), try getting communication to run from that computer – if it works from one computer and not another, you successfully narrow down the problem to the computer itself, rather than a POS hardware or cabling issue

We hope these suggestions give you some ideas to work with when trying to resolve network communication issues.  While we do our best to provide guidance where we can, POSLynx cannot be solely responsible for fixing communication problems remotely – at times, you may need local technical assistance to get your computer, network and POS terminals communicating properly and consistently.

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