Android app client sending problem.

Hi i have problem with android client app on my smartphones, when it's connecting to my WiFi i have information "Send failed"
if i turn off WiFi client app imediely send data do server by GSM data and i have infomation "connected to network" but the problem keeps coming back when i again connect to my WiFi. Please help me.

Sounds like server connection fails through WiFi. Most likely some network issue.

Please can You tell me where to look for the problem.

Already told - in your network, most likely.

I have found reason of my problem, I've enabled NAT Loopback in my router and now everything is working fine.