Mitsubishi L02CPU User Manual page 86

(6) Precautions for file access during communication
The CPU module will perform file access processing prior to Ethernet communication processing. Because of
this, processing of the socket communication function may be delayed if a file is accessed by FTP or a
programming tool during the processing.
When accessing a file while response time monitoring is performed on the connected device with the socket
communication function, add the time required for file access to the monitoring time.
(7) Checking receive data length
Since no delimiter is provided for TCP communication data, on the receiving end, separate data blocks that are
sent continuously may be combined, or data sent all at once may be segmented. The receive data length must be
confirmed on the receiving side as necessary.
When data are received on the CPU module side and the data length is determined, the fixed-length mode is
recommended.
When receiving data on the target device side, confirm the receive data length as shown below.
Receive the rest of the message.
(8) If an error (error code: 41A0
In TCP communications, if an error (error code: 41A0
sent. Therefore, if the data are sent again after the error (error code: 41A0
data. Then open a connection again, and send the data again.
84
Receive processing on the other device side
Received message, receive processing
Is TCP connection open?
YES
Received data within
the time specified by the monitoring
timer value?
YES
Check the received data size.
NO
Sufficient receive data size?
YES
Processing for the received message
Was the entire received
message processed?
YES
End
) has occurred
H
) occurs at the sender, part of send data may have been
H
NO
TCP connection is closed.
NO
NO
Error handling
), close the connection to discard the
H