duplicate request while sending in json

Question

hi

 

please find attached my code .i am send 1000 no in json to client but client sometimes getting 1000 sometime 2000 ,3000 nos due to which duplicate request is going also

 

i am getting error of sometimes 400 bad request from server .client is saying i m sending null sometimes but i m nt sending null in json array

 

please chk my code and rectify it .its urgent