Questions about receiving IDXP message

Hi, everybody!

When I send several txt messages via rr_idxp_send() continually, 
the server can recv the data correctly only on condition that the 
original message payload is less than one variable value. 
For example, if I send the message with the length of 20 bytes for 10 
times, the server will crash; while I send the 20 bytes for 3 times, 
then it works well.
Then we try to add the interval between every other message, when the 
interval is more than about 31ms, the server can process the message 
fluently, independent of the message size.

Another problem occurs when I test the message with different sizes. 
The server can recv only 4164 bytes while the client sends the messages 
with the approximate length from 5000 to 8000 , which is so strange. 
At the same time, all behaves well when the length is less or more. 
I am so puzzled about it.

Can you help to explain these case, and give some recommendation on 
the solution. Thank you all!