Webrequest Suddenly Doesn't Work

 
I have an EA where it sends Webrequest every few seconds. The EA would run for a few hours, then suddenly the webrequest would just stop working. I have set the Webrequest to have 3000ms (3 seconds) timeout, but when it stop working, it would just abruptly gives -1 error and getlasterror will show 5203 (receive response failed), without waiting for 3 seconds.