Simulate a proxy or server that is silently dropping pooled tcp connections?

Question

We have a system whereby we make a RESTful callback to a client's remote server. We are seeing timeouts waiting for a response when a request has apparently been sent. Some constraints:

1. it is difficult to get hold of TCP dump logs outside of the server, elsewhere on the local network.
2. We do not have access to the client's system.

We think that, when traffic is low, the remote proxy is killing idle connections without telling us. I have added a reaper thread for idle connections. This should have been in there already and adding it is an improvement to the system. However, I still would like to simulate the error condition on our local network and that has proven a little tricky. Our test server, a servlet container, is well-behaved in that it is correctly closing TCP connections.

How should I go about creating a setup whereby:

1. idle connections are dropped without further TCP traffic
2. further traffic relating to those connections is ignored?

Answer 1

You could put in a router with NAT or a firewall between, and set the TCP timeout to be very low.

Alternatively, you could try to correct the situation by using TCP keepalive. This will periodically send TCP ACKs with no data in order to keep the TCP session open.