UDP Socket Programming

I am using UDP Server which receives data through port 50001. I used wireshark to monitor the data. Here the data what i receive in UDP server buffer and what data is showing in wireshark is not matching fully . but some places it is matching exactly ...What could be the reason for this? here is the receiver code for UDP server

char mesg[50];


n=recvfrom(sockfd,mesg,50,0,(struct sockaddr*)&cliaddr,&len);
fwrite(mesg,1,50,fp);

the values whatever is coming from client should be in the range of 3000 to -3000 but in some places it is going to 30000 to -30000. In wireshark i plotted that values it is coming exactly in 3000 to -3000 range. but if i plot the received buffer it is giving in the range of 3000 to -3000 but also more values are in the range of 30000 to -30000

Tags: C++, C, VC++, MFC