Moxa Technologies IA5150 User Manual

Page of 108
NPort IA5150/5250 Series User’s Manual 
Choosing the Proper Operation Mode 
 
4-4
TCP Client Mode 
In TCP Client mode, NPort IA5150/5250 can 
actively establish a TCP connection to a 
pre-defined host computer when serial data 
arrives. 
After the data has been transferred, NPort 
IA5150/5250 can automatically disconnect from 
the host computer by using the TCP alive check 
time
 or Inactivity time settings. Refer to Chapter 
5 for more details. 
As illustrated in the figure, data transmission 
proceeds as follows: 
1.  The NPort IA5150/5250 configured for TCP 
Client Mode requests a connection from the 
host. 
2.  Once the connection is established, data can 
be transmitted in both directions—from the 
host to the NPort IA5150/5250, and from the 
NPort IA5150/5250 to the host. 
TCP Client Mode
1Request a
   connection
2Proceed with
   data transmission
TCP Client
RS-232/422/485
1
2
Device
TCP/IP
Ethernet
UDP Mode 
Compared to TCP communication, UDP is faster 
and more efficient. In UDP mode, you can unicast 
or multicast data from the serial device to one or 
multiple host computers, and the serial device can 
also receive data from one or multiple host 
computers, making this mode ideal for message 
display applications. 
RS-232/422/485
Device
TCP/IP
Ethernet
Directly proceed with
data transmission
(no connection required)
UDP Mode
Pair Connection Mode 
Pair Connection Mode employs two NPort IA5150/5250 in tandem, and can be used to remove the 
15-meter distance limitation imposed by the RS-232 interface. One NPort IA5150/5250 is 
connected from its RS-232 port to the COM port of a PC or other type of computer, such as 
hand-held PDAs that have a serial port, and the serial device is connected to the RS-232 port of the 
other NPort IA5150/5250. The two NPort IA5150/5250 units are then connected to each other 
with a cross-over Ethernet cable, both are connected to the same LAN, or in a more advanced 
setup, they communicate with each other over a WAN (i.e., through one or more routers). Pair 
Connection Mode transparently transfers both data and modem control signals (although it cannot 
transmit the DCD signal) between the two NPorts.