Delays in LAN Operations

This page describes several different problems related to delays in LAN operations.

Problem: Delay in Find Interfaces Operations

You are experiencing long delays (up to five minutes) during a search for new interfaces/instruments, when you are adding a remote serial instrument, remote GPIB interface, or remote USB interface in Connection Expert.

Probable Cause:

A remote interface is busy because it is being accessed by another process.

Suggested Steps:

  1. Launch Connection Expert from the IO Control.
  2. Select and edit the LAN interface in question.

  3. Check the Connect Timeout and Client Delta Timeout properties of the TCPIP (LAN) interface associated with the remote interface you are adding. The default values for these are both 5000 milliseconds; that usually results in acceptably short delays (10 to 20 seconds). If you have upgraded from a previous version of the IO Libraries Suite, the Client Delta Timeout may be set to 25 seconds (25000 milliseconds). Reduce this value to 5000 milliseconds.
Disable the firewall for the working of Find Interfaces functionality on Linux systems.
Windows on ARM does not support Serial Interface, Serial Instrument, GPIB Interface, GPIB Instrument, Remote GPIB, Remote Serial, and Remote USB

Problem: Delay when Using Hostname

You are experiencing delays (up to 30 seconds) when opening a LAN device using its hostname.

Probable Cause:

This may be caused by the Domain Name Service (DNS) topology on your network.  DNS servers communicate with the client machine and with each other to resolve a hostname to an IP address on the network. Delays can occur if multiple DNS servers must be contacted to resolve the hostname.

Suggested Steps:

  1. Specify the IP address rather than the hostname.

  2. Alternatively, add the hostname to the local computer’s hosts file.  Do not do this if the device you are accessing uses DHCP (Dynamic Host Control Protocol) to obtain an IP address.  In this case, the device’s IP address may change without notice, in which case you will not be able to communicate with it or may end up communicating with the wrong device.

Problem: Delay when Opening a LAN Device

You are experiencing delays when attempting to open LAN-based devices (such as LAN instruments and LAN-to-GPIB gateways) in VISA or SICL.

Probable Cause:

You may not have your LAN configured properly for DHCP and DNS.  If your computer is configured for DHCP, but there is no DHCP server available, the computer will attempt to contact the non-existent server for up to 150 seconds before timing out.  Similarly, if your computer is configured for DNS but no DNS server is available, you may see timeout delays when attempting to open an LAN device.

Suggested Steps:

  1. Move your computer to a network without a DHCP or DNS server to determine whether DHCP or DNS configuration is the problem. 

  2. If you still experience delays, make sure your network configuration is correct, then reboot to make sure your computer is not attempting to use settings remembered from its original network connection.