Rockwell Automation 1768-EWEB EtherNet/IP Web Server Module User Manual - Manual (Page 130)

Publication ENET-UM527E-EN-P - October 2006
130 Socket Interface
Typical Sequence of Transactions For UDP Without
OpenConnection
The following diagram shows a typical sequence of socket interface
transactions for UDP communications without using the
OpenConnection service to specify the destination address. In this
case, the Logix controller specifies the destination for each datagram
and receives the sender’s address along with each datagram it
receives. Each transaction between the Logix controller and the web
server is a MSG instruction.
The example below shows the Logix controller sending data to a
device and then the device sending a response. This is a typical
sequence of transactions. Depending on the application protocol, the
device could instead initiate sending data to the Logix controller.
Additionally, each Write does not require an application response or
acknowledgement. The application protocol determines the exact
sequence of application transactions.
Logix
controller
Web Server Module
10.10.10.10
Device
10.10.10.11
CreateSocket
Port=49100
CreateSocket
Response Instance =
102
Write
10.10.10.11?Port=49200
Data = abc
Write Response
Read
Read Response
10.10.10.11?Port=49200
Data = xyz
Send Data To
10.10.10.10, Port 49100.
Receive Data From
Port 49200.
Data = abc
Data = xyz
The response is returned to the
controller as soon as the data is sent.