i need it for legit purpose. in unity some web requests are obvious. like www requests. but some others like iab and google play services can not be traced are find out what they are. is there any tool or app to find out what data is being sent and received?

thank you for helping. 

Most people find Ethereal to be quite helpful. If the app runs on a separate device (phone, etc) you may need to insert yourself as a proxy to see the packets. And if the protocol uses TLS, you also need the certificates to be able to decode the payload.

Another option is to install/use libpcap on the device in question. (This is like the tcpdump tool, in a library.) Then capture the pcap log and analyze it in Ethereal.

Finally, you can use tricks like LD_PRELOAD to insert a library that implements the networking API, and captures the data before it's handed off to the sockets. How this works, depends on which OS/device you're using.