Mitsubishi MELSEC L Series User Manual page 58

(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 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.
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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
NO
TCP connection is closed.
NO
NO
Error handling