Chapter 6
Using Your Serial Device Server
ENET-232 and ENET-485 Series User Manual
6-2
ni.com
NI-VISA also has a graphical API as part of LabVIEW, a National
Instruments graphical programming environment. For Solaris, National
Instruments offers LabWindows/CVI, which provides an interactive
ANSI C programming environment for building virtual instrument
applications. The National Instruments Web site,
ni.com
, includes
more information about these environments.
Using DHCP
The Dynamic Host Configuration Protocol (DHCP) is designed for large
networks in which networking devices are transient and network
parameters cannot be statically assigned and thus tied to specific devices.
DHCP eases the addition of networking devices onto a network by having
a server assign necessary network parameters, including the IP address,
netmask, and router information, to a newly attached network device.
Optionally, if the device provides a hostname with the configuration
request, DHCP may attempt to configure your network to recognize the
device with the requested hostname.
DHCP requires a Domain Name Server (DNS) to associate the numerical
IP address assigned with the requested hostname. Within the past few years,
an Internet community standard has emerged to provide a standardized way
for these services to provide dynamic domain name services. Using this
standard, after DHCP assigns the numerical IP address, it can communicate
with DNS to register the newly assigned IP address with the requested
hostname. However, the complexity of DHCP and dynamic name
registration typically requires active management by a corporate MIS
department, or equivalent, because of several risks for failure.
One possible failure can occur if the pool of available addresses contains no
more unassigned IP addresses. This problem is evident if DHCP fails to
work and the
PWR/RDY
LED continues to flicker for longer than
90 seconds at power on. In this situation, you need to obtain a static
IP address from your network administrator and configure the device
yourself using NI Ethernet device configuration, as described in Chapter 3,
. Notice that if DHCP fails to assign you an address,
the current subnet might not have an address available for you to use. In this
case, you may need to move your product to another subnet where there is
an available IP address.
Failure also happens if communication between DHCP and DNS does not
occur. In this situation, DHCP assigns an address to the device, but you
cannot communicate to it using the hostname you assigned. Your network
administrator may need to insert the hostname manually into the DNS
