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Basic Networking & Troubleshooting (App Note)

This application note exists to provide a basis for more detailed discussion, and also help beginners with network setup and configuration. Some troubleshooting steps for common networking problems are also included at the end.

 

General Terms

For the sake of a quick disambiguation, basic functionality of each component is listed below.

  • Modem - Connects a local network to the internet by linking to internet provider infrastructure.
  • Router - Provides gateway/firewall for the internet. Routes traffic from each PC or other device on a local network to the appropriate location. Most routers can also act as a DHCP server, which allows them to grant IP addresses for DHCP enabled network devices. If it is a wireless router, it also includes a wireless access point which creates a WiFi network that has a name (SSID), password, and a type of encryption (WPA, WPA2, WEP, etc).
A modern wireless router includes several basic components

Figure 1. Modern wireless router with DHCP server, multiple Ethernet ports, integrated wireless access point, and gateway.

  • Switch/Hub - Expands total available Ethernet jacks.
  • Bridge - Connects multiple network segments, which are physically or logically (by protocol) separate. Bridges connect to wireless access points.
  • Wireless Access Point (AP) - Creates a WiFi network that has a name (SSID), password, and a type of encryption (WPA, WPA2, WEP, etc).
  • Mobile Hotspot - When generated by a cell phone, it is a wireless access point, DHCP server, and a modem all-in-one. Internet access is gained through the cell network (3G, 4G etc).
  • Subnet - A group of computers and devices which share a common IP address component. Subnets are often designed to correspond with physical computer groupings. A single small building, house, or department will usually just be a single subnet. For instance, 192.168.1.* designates a subnet of 192.168.1
  • DHCP Server - Assigns IP addresses to client computers. Keeps track of the "pool" of available IP addresses.

 

Typical Home/Small Office Network

The most common way to setup a home or small office network is to buy a wireless router, and just connect everything to it. When there are no longer any available LAN ports on the router, it's possible to expand the number of LAN ports with a simple switch/hub. Figure 2 shows how a LabJack device will typically be connected in this type of network.

Typical Home/Small Office Network with Labjack T7 and T7-Pro

Figure 2. A typical small home/office network.

In Figure 2 above, the computer controlling the LabJack device is referred to as the "Host". The host sends/receives data to/from the LabJack device by using the device's IP address. In order for communication to work, both the host computer and the device need to have a unique IP address that is valid on the network.

  

Static IP vs Dynamic IP (DHCP)

Each device/host on the network has a unique numerical IP address.  Other things on the network use that address to connect to and talk with that device/host.  There are two standard ways of obtaining an IP address. 

  1. Static IP - The device/host always has the same manually assigned IP address.  For instance, your router might have the static IP of 192.168.1.1, meaning the router is always reachable at that address. 
  2. Dynamic IP - The DHCP server (typically the router) assigns each device/host on the network a unique IP address. The DHCP server also keeps track of the "pool" of available IP addresses, so that if a computer is removed from the network, its IP address can be reused.

The advantage of the static IP is that it is always the same, but the disadvantage is that you have to assign it to the device/host and it must be unique.  If two devices are assigned the same IP, conflict will occur when both devices are ON.  By using DHCP you ensure that each IP is unique (since the DHCP server assigns them that way) but you have to find out which IP address was assigned to a device/host before you know which IP address to use to talk to it.  Our Ethernet/WiFi LabJack products support both static IPs and DHCP.  DHCP is convenient, but not all networks allow searching to find devices and searching is slower than a specific open, so static IPs are usually best for the end user's production applications.

 

Setting up a LabJack Ethernet/WiFi Device

The first step to connecting an Ethernet or WiFi LabJack device is to connect it to the computer using USB, and configure the IP, Subnet, and Gateway according to your particular network.

 

UE9 Setup

1.  Connect the UE9 over USB, and open the LJControlPanel application.

2.  Enter the IP Address, Subnet, and Gateway parameters in LJControlPanel. Enable DHCP if you want to automatically get a unique IP address. For DHCP to work, the UE9 Ethernet must be connected to an operational network, like Figure 2.

UE9 and UE9 Pro TCP network setup via LJ Control Panel

Figure 3. UE9 IP configuration in LJControlPanel

3.  Then click "Write Values" to make the change permanent. After changes are saved, LJControlPanel will prompt to reset the device.

4.  Finally, make sure the UE9 Ethernet is connected to an Ethernet jack on the network, and Click "Find Devices" again to verify that the device exists on the network.

UE9 and UE9 Pro TCP network setup verification

Figure 4. UE9 IP configured successfully

See the 'Troubleshooting UE9/T7' section below, or the UE9 Ethernet Test App page if there are problems.

 

T7/T4 Setup

See the Setup WiFi and Ethernet for the T7 and T4 App Note.

 

Setting up a Wireless Access Point

As stated above, a wireless access point (AP) is just a wireless link into the network. The most common configuration is shown in Figure 2, where the router creates an AP, and WiFi devices connect to the AP. Access points are configured with the following parameters:

  • SSID - Also known as the "Name" of the wireless network. Devices will associate themselves to the network using this name.
  • Authentication - WEP (old), WPA, WPA2, WPA2-PSK, WPA2-ENT. Typically people use WPA2, or WPA2-PSK. We recommend WPA2, since we primarily test our devices with WPA2.
  • Encryption -AES or TKIP (most likely others). 
  • Password - Self explanatory. Some encryption methods require 8 or more characters.

The T7's WiFi chip only supports the following authentication/encryption pairs (We highly suggest using WPA2-PSK with AES encryption):

  • WEP-64 and WEP-128 (open mode only, NOT shared mode)
  • WPA2-PSK (AES only).  This is the recommended configuration.  Other authentication/encryption options are not as secure and may not work properly.
  • WPA1-PSK (TKIP only)
  • WPA-PSK mixed mode (some access points, not all are supported)

1.  Connect a computer to one of the LAN Ethernet ports on the back of the router.  Note: Do not use a WAN, or Internet Ethernet port.

2.  Launch a web browser and enter one of the following in the browser's address bar:

  • routerlogin.com
  • routerlogin.net
  • Access point default IP address, e.g. "192.168.1.1"
You are prompted to log in

3. Enter your username and password.  Defaults are commonly admin/admin, or admin/password.

4. Specify SSID, Encryption, and Password, and enable the wireless network. Save or apply the changes.

Note:  If you are configuring a router to be an access point only (not using it for internet, or DHCP server), then you should disable anything relating to "DHCP Server" or "Internet".  This is shown in figure 2 of the Expanded Networks section of the Advanced Networking App Note.

 

T7-Pro Direct to Computer via WiFi

Wireless access points can also be created by some devices, such as tablets, cell phones, and laptops.  Figure 8 demonstrates a cell phone that is configured as a Mobile Hotspot, which is just an access point that provides mobile internet access. The Laptop communicates with the LabJack T7s, and is therefore considered the "Host" of the T7s.  The cell phone is acting as a relay for signals, but is not itself communicating with the LabJack devices.

 

Mobile hotspot/AP (access point), two T7-Pros, and a laptop host

Figure 8. Mobile hotspot (AP), two T7s, and a laptop host

Figure 9 demonstrates a laptop that is configured as an AP. Configure a laptop as an access point by using special software, or natively in Windows 7 and other new operating systems. Several virtual access point programs can be found through Google.

Laptop access point (AP) and host, with two T7-Pros

Figure 9. Mobile hotspot (AP), two T7s, and a laptop host

 

In our experience we have found that some virtual APs just do not work.  Sometimes they will even allow a smartphone to connect, but for whatever reason are not compatible with the WiFi module in the T7-Pro.  The problems are noticed right at the start when you create a new access point and have the T7-Pro try to join it.  If it does work and the T7-Pro joins the network it is generally as reliable as any other WiFi network.  For more help see the troubleshooting tips towards the end of the Basic Networking & Troubleshooting App Note and also the WiFi specific troubleshooting tips on the Setup WiFi and Ethernet for the T7, T4, and T7-Pro App Note.

Some options to consider:

1.Try the VAP included with Win 7 or newer.  For Windows 10 you need to have the August 2016 Windows Anniversary Update:

http://www.howtogeek.com/214080/how-to-turn-your-windows-pc-into-a-wi-fi...

2.  Try 3rd-party VAP software.  In our most recent testing mHotspot worked best.  We also had success with Connectify.

3.  If neither #1 or #2 work with the built-in WiFi adapter on your laptop, disable that adapter and add a new adapter to try.  We tested the TL-WN725N with success, but the best option (also tested successfully) might be the Aukey WF-R13 wireless adapter and their provided software.  Aukey provides a program called "Mediatek Wireless Utility" that enables you to configure the Aukey WF-R13 wireless adapter as a wireless access point with a customized SSID name, WiFi channel, and WPA2-PSK authentication using AES encryption.

4.  Use an external access point (i.e. router) giving you Figure 2 above.  There are very small ones that could go near the T7-Pro or near the laptop.  The computer and T7-Pro can both connect to the access point by WiFi or Ethernet.  The ideal solution is often to put the access point near the T7-Pro and make that connection via Ethernet, as the Ethernet connection on the T7-Pro is much faster than WiFi (and this works with the normal T7 as well as the T4).

5.  Use the Ethernet connection on the T7 or T4 to connect to a nearby Ethernet-WiFi bridge.  This has the added advantage of high data rates, as an external wireless bridge should support full Ethernet speeds.  See the Convert Ethernet to WiFi App Note.

 

WiFi AP troubleshooting: After reading a few articles and hearing about several customers having WiFi AP issues where the T7-Pro was not able to connect to an access point hosted by a computer, there may be a particular feature required by the T7-Pro's WiFi chip that not all wireless adapters have.  In other words, not all wireless adapters are created equal.  If you want to host a wireless access point that the T7-Pro can connect to, the network card likely needs to have a "Soft AP" capability.  On Windows 10, you can type the command "netsh wlan show wirelesscapabilities" into a command prompt to list the available wireless adapters installed on the computer and what capabilities it has.  The "Soft AP" mode should list "Supported" next to it.  The T7-Pro may not be able to connect to all created ad-hoc networks but can most likely connect to all created SoftAP networks, especially when they offer WPA2-PSK authentication using AES encryption.

Another useful command is "netsh wlan show interfaces" which prints out a list of WiFi interfaces and their status which indicates signal strength and network speed.

Setting up WiFi AP (Soft AP, Ad-Hoc, etc.) Sources:

 

Default LabJack Device IP Addresses

T7 Ethernet   192.168.1.207
T4 Ethernet 192.168.1.214 T7-PRO WiFi 192.168.1.217 UE9 Ethernet 192.168.1.209

 

UE9/T7 Ethernet Troubleshooting

These are the most common problems for not being able to connect to a LabJack device on your network, and how to solve them.  Many of these also apply to WiFi connections, but there are additional T7-Pro WiFi specific troubleshooting tips at the end of Setup WiFi and Ethernet for the T7, T4, and T7-Pro App Note.

 

1.  Some basics:

Make sure you are up-to-speed on these basic items first, and in the event you need to contact us you can start by letting us know you have done the "Basic Networking Troubleshooting #1" items.

  • Install the latest software package.  In fact, to match what we are running please use the latest beta version if there is one.
  • Update to the latest firmware.  Again, to match what we are running please use the latest beta version if there is one.
  • Make sure you are only running 1 software application at a time.  Don't run Kipling and LJLogM at the same time, for example.  Even close Kipling before running Ping.  T-Series devices have limited support for multiple sockets, and it is certainly possible to just disconnect from a connection in Kipling rather than closing Kipling, but to avoid confusion during troubleshooting only run 1 application at a time.

 

2.  Determine what is working and what is not:

Use Ping to see if you have basic communication, as described in step 8 (Ethernet) or 14 (WiFi) on the Setup WiFi and Ethernet for the T7, T4, and T7-Pro app note.   Do other types of opens (Native TCP, LJM Search, and LJM Specific) to see which work and which do not, as described in step 9 (Ethernet) or 15 (WiFi) on the Setup WiFi and Ethernet for the T7, T4, and T7-Pro app note. 

  1. Ping does not work.  Suggests that even UDP is likely not working.  Start with items #11 & #12 below, and then look at the rest of the items.
  2. Ping works, but Specific Open does not work.  Suggests that UDP is working but TCP is not.  Usually an issue with network and TCP configuration.  Start with item #3 below and look at items #4-#8 as needed.
  3. Specific Open works, but Search Open does not.  Suggests that the connection is totally working, but the search technique used by LJM cannot find it.  See item #9 below.

 

3. The IP address is not valid on the subnet:

Open a command prompt window and type "ipconfig" to see a listing of the IP address and subnet mask for a particular PC. If the PC shows a subnet mask of 255.255.255.0, that means it can only talk to devices with the same first 3 bytes of the IP address. The default IP addresses of LabJack devices are shown above, and they generally work on a network using the 192.168.1.* subnet (unless another device is already using the address). If the IP address of the LabJack device needs to be changed, the easiest way is via USB with the LJControlPanel (UE9) or Kipling (T-Series) application.

Does it make a difference whether you use a dynamic IP (DHCP) or static IP?

Tip:  It can be useful to send 2 things to us to help you troubleshoot:

  • Send the output of ipconfig from your computer.  Right-click on the little icon in the upper-left of the title bar of the Command Prompt window, and choose Edit => Select All.  Then right-click again and choose Copy.  Now you can paste the info into an email.
  • Use LJControlPanel (UE9) or Kipling (T-Series) to connect over USB, go to a screen that shows the Ethernet settings of the device, and to <Alt-PrintScreen> to grab a screenshot and send that to us.

 

4. Something else is using the same IP address:

Disconnect the LabJack device and ping the IP address in question to see if anything responds. For example, to ping the default UE9 IP address, open a command prompt window and type "ping 192.168.1.209".  If the LabJack is not connected there should be no response.

 

5. Trying to use DHCP when there is no DHCP server available.

This problem is common in a peer-to-peer network.  That is, with a direct Ethernet connection from the LabJack to the host.  The LabJack does not have a DHCP server, and most likely the host does not either, so you need to configure both the LabJack and the host to use valid (different) static IPs.

 

6.  TCP stack not initializing properly with a static IP:

Some firmware versions before 1.0217 had a problem such that the TCP stack did not start up properly when using a static IP.  It would work correctly when initially configured in Kipling, but then sometimes not work after a reboot.  Make sure you are running firmware 1.0217 or higher.

 

7. Cannot communicate between WiFi and Ethernet device/host:

Check to see if the wireless access point (typically a router) has wireless isolation enabled. If wireless isolation is enabled, it will prevent an Ethernet computer from being able to detect or communicate with a WiFi device on the wireless network, because the WiFi stuff is isolated from the Ethernet stuff, and vice versa.

 

8. Firewall software on the host is blocking traffic or closing the connection:
Try closing or disabling software related to firewalls or anti-virus.

For example, on Linux, if a Wireshark capture shows ICMP messages with "Destination unreachable (Host administratively prohibited)" related to port 502 or port 52362, try disabling the firewall as root:

# /etc/init.d/iptables save
# /etc/init.d/iptables stop

You can re-enable your firewall with:

# /etc/init.d/iptables start

For more about Linux firewalls, see this nixCraft post on how to disable the firewall in Linux.

 

9. Perhaps the TCP connection is fine, but search does not work?

Kipling and LJControlPanel (via ListAll function) use a UDP broadcast search technique to attempt to find all T7s, T4s, or UE9s on the network, but with some networks this does not work and a direct TCP open must be done.

UD library (UE9):  In LJControlPanel go to Options=>Settings and add specific IPs that LJCP will try to open directly.  At the UD API level search is used by ListAll, so instead use OpenLabJack with the specific IP address of the UE9 to see if a direct TCP open works.  In LJLogUD or LJStreamUD, you can force a direct TCP open (rather than a search) by editing the _open.cfg files as described on either page.

LJM library (T-Series):  As of version 1.15 (May 4th, 2017) the LJM library automatically stores network connection information to the auto IPs file to help open connections to LabJack devices. IPs can also manually be added to LJM Specific IP configuration to tell LJM particular IP addresses on which to try a direct open. Both auto IPs and specific IPs affect not just Kipling but all ListAll and Open calls on that machine.  You can also just do a direct TCP open in your software by calling one of the Open functions and passing a specific IP address (e.g. "192.168.1.207") for Identifier rather than passing "ANY".  In LJLogM or LJStreamM, you can force a direct TCP open (rather than a search) by editing the _open.cfg files as described on either page.

Attached to this page is a Windows application called TCPOpenTesting.  For LJM (T-Series) testing use this to try 3 different types of opens:  native direct TCP (left side of application), LJM search open (middle of application with any/any/any), and LJM specific open (middle of application with specific parameters such as t7/ethernet/192.168.1.207).  For UD (UE9) testing use this to try 2 different types of opens:  native direct TCP (left side of application) and UD specific open (right side of application with specific parameters such as LJ_dtUE9/LJ_ctETHERNET/192.168.1.209/FirstFound=FALSE).

 

10.  Ethernet connection only shows up in Kipling when USB is connected also.

This is usually a symptom of #9 above.

 

11. Connection not electrically valid:

With the UE9, check that the correct Ethernet cable connected. The UE9 does not support Automatic MDI/MDI-X, so if the device on the other end of the cable also does not support Automatic MDI/MDI-X (a rare situation these days) then a crossover cable might be required.

Try a different Ethernet cable.

Ensure that the switch/hub/NIC supports 10Base-T for the UE9, whereas the T-Series devices support 10Base-T or 100Base-T.

Use the LEDs on the switch/hub/NIC to determine if you have an electrically valid connection. An orange LED is often used to indicate a good 10Base-T connection, but consult the manual for the switch/hub/NIC to be sure. If there is any communication at all, such as ping, then you know the connection is electrically valid.

Make sure the LabJack device has power.  Do you see normal activity on the COMM and STATUS/CONTROL LEDs?

With the T7 or T4, look at the LEDs on the Ethernet connector for correct activity.

Check that the pins inside of the Ethernet jack are not bent downward or otherwise damaged (see images below). Forcing a USB cable into the Ethernet jack can cause damage such as shown below:


A normal, good Ethernet jack
 A bad Ethernet jack with bent and deflected pins

Try wiggling the Ethernet cable near the Ethernet jack or applying upward pressure to see if that causes any LED activity.

 

12. The LabJack device has been damaged and does not work at all:
Use a USB connection to test basic functionality. Confirm proper LED behavior as described in device datasheet. Confirm installation and operation using the quickstart guide for the device.

  

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