Omron Sysmac NJ-series User Manual

9-3
9 Socket Service
NJ/NX-series CPU Unit Built-in EtherNet/IP Port User’s Manual (W506)
9-2 Basic Knowledge on Protocols
9
9-2-1 Differences between TCP and UDP
9-2 Basic Knowledge on Protocols
The TCP and UDP functions used on socket services differ as shown below.
The following operations are performed each time data is sent to ensure that it reaches the destination
node. The destination node returns an acknowledgement (ACK) when data is received normally. The
sending node sends the next data after ACK is returned. It resends the same data if ACK is not
received within a certain length of time.
In TCP, the remote IP address and the remote TCP port number are specified when a request is made
to open a socket. The variables that store the data to send are specified when the send request is
made.
Data is simply sent to the destination node and no acknowledgement or resends are performed like
they are for TCP. To increase the reliability of communications, the user application must perform data
resend processing.
In UDP, the remote IP address and the remote UDP port number are not specified when a request is
made to open a socket. The variables that store the remote IP address, the remote UDP port number,
and the data to send are specified when the send request is made. (The received data is stored in the
response data to specify which UDP port was used from which IP address.) Furthermore, once a
socket is open in UDP, communications with other remote nodes is possible even if the socket is not
closed.
9-2-1 Differences between TCP and UDP
TCP Communications
UDP Communications
Destination node
Receive
request
Sending node
Resend data
If ACK is not returned
Acknowledgement (ACK)
Send data
Send
request
Destination node
Acknowledgement (ACK)
(When ACK processing is performed by user application)
Sending node
Send
request
Receive
request
Send data

Omron Sysmac NJ-series Specifications

General

Brand	Omron
Model	Sysmac NJ-series
Category	Computer Hardware
Language	English