Fragmenting Of Send Data - Omron sysmac NX102-9 Series Owner's Manual

9-2-2

Fragmenting of Send Data

The receive buffer for the built-in EtherNet/IP port is a maximum of 9,000 bytes per socket handle. If
any data that is larger than 9,000 bytes is received, any data over 9,000 bytes is discarded.
Up to 2,000 bytes can be received for a single request. In this case, the data is sent in fragments as
described below.
Using TCP
The conditions shown in the following figure occur when data is sent in fragments in TCP communica-
tions.
(1) A send request is sent from the user program at the sending node. It specifies a vari-
able with a data length of 2,000 bytes.
(2) The built-in EtherNet/IP port separates the send data into 1,024 bytes in data A and
976 bytes in data B.
(3) Data A and data B are sent in sequence by the sending node.
(4) After data A is received, the remaining data B is received.
Sending node (Controller)
User program
(1) Send request
2,000 bytes
Original data
Data in TCP communications is delivered to the user program in a fragmented form, as shown
above. The number of bytes of data that is received must be checked to confirm all data was
received before the next receive request is made. (You can use the RecvDataSize output variable of
the socket receive request instruction to check the received data.)
NJ/NX-series CPU Unit Built-in EtherNet/IP Port User's Manual (W506)
Built-in
EtherNet/IP port
Ethernet line
(3)
(2) Fragmenting
Data A and
data B are
1,024 bytes
sent in
succession.
Data A
Data B
976 bytes
Receiving node (host computer)
Receiving node User program
(4) Receive request
2,000 bytes
Data A Data A
1,024 bytes
(5) Receives remaining 976 bytes.
2,000 bytes
Data B Data B
976 bytes
(6) Receive request
(request for 2,000 bytes)
9 Socket Service
9-5
9