What causes a TCP/IP reset (RST) flag to be sent?
I'm trying to figure out why my app's TCP/IP connection keeps hiccuping every 10 minutes (exactly, within 1-2 seconds). I ran Wireshark and discovered that after 10 minutes of inactivity the other end is sending a packet with the reset (RST) flag set. A google search tells me "the RESET flag signifies that the receiver has become confused and so wants to abort the connection" but that is a little short of the detail I need. What could be causing this? And is it possible that some router along the way is responsible for it or would this always come from the other endpoint?
Edit: There is a router (specifically a Linksys WRT-54G) sitting between my computer and the other endpoint -- is there anything I should look for in the router settings?
Answer
A 'router' could be doing anything - particularly NAT, which might involve any amount of bug-ridden messing with traffic...
One reason a device will send a RST is in response to receiving a packet for a closed socket.
It's hard to give a firm but general answer, because every possible perversion has been visited on TCP since its inception, and all sorts of people might be inserting RSTs in an attempt to block traffic. (Some 'national firewalls' work like this, for example.)