Campbell Scientific NL200/NL201 Network Link Interface - Manual (Page 49)

Appendix C. NL200/201 Settings
connection with the remote server and if the connection fails to open, the
device will continue to retry at an interval of 60 seconds. If data arrives on
the RS-232 port when no TCP connection exists, the device will buffer up
the data (up to 1500 bytes) and immediately attempt to open a connection
to deliver the data. If the remote server closes the connection due to error,
the device will make a best effort to save any data that was in process and
re-queue it to be sent on the next successfully-opened TCP connection.
PakBus
This port uses the PakBus® protocol.
Modbus/TCP Gateway
The device will listen for incoming MODBUS/TCP connections from a
remote client. The port number of the listening connection is specified in
the “RS-232 Service Port Number” setting. The device will convert
incoming MODBUS/TCP frames to MODBUS/RTU and forward them to
the RS-232 port. The device will wait for a response from the
MODBUS/RTU device and forward the response back to the remote
MODBUS/TCP client over the established TCP connection.
Disabled
This port will not be used.
RS-232 Service Port Number
This setting is used when the RS-232 port is configured as a Serial Server or
MODBUS/TCP gateway. To communicate with a TCP/IP server, the client
application must open a socket to that server. The socket of a specific server is
uniquely identified by an IP address of the host where the server is running and
a port number associated with the server application on that host. This entry is
where the port number of the server is set. Ensure that the client application is
set to use the same port number as configured here. Most MODBUS/TCP
applications use port 502. (range 1..65535)
RS-232 Baud Rate
This setting specifies the baud rate of the RS-232 port. The connected device
must be set to communicate at the same baud rate.
RS-232 RTS
The NL200/201 asserts the RTS and DTR lines when doing RS-232
communications. This setting allows the user to disable the RTS line if needed
so that it will not be asserted. Some hardware will not function if the RTS line is
asserted, but typically, it is not necessary to change this setting from its default
(enabled).
RS-232 TCP Timeout
This setting will determine how fast the device will timeout on the open TCP
connection. For Serial Server and MODBUS/gateway configurations the
device will close the TCP connection if no activity is detected for the timeout
period. For the TCP Client configuration the device will close the TCP client
connection if no activity is detected and then immediately open another
connection with the remote server. This behavior helps to ensure that the
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