Ask Software Development Questions and Get Answers ASAp
If you've been a UNIX admin for many years, you should be able to run ps -efl (unless it's ps-axl on your variant) and find what firewall is running.
Then again, there could also be some kernel module installed that is working with ipchains or pcap or some such.
It can be extremely difficult to track down these kinds of things. That having been said, one presumes that an out-of-the box firewall is not configured to "block everything not explicitly permitted," as that would make operation extraordinarily cumbersome.
When you flushed routing tables, did you empty anything else?
If things are running well, why would you go flushing tables? Lord only knows what kind of inconsistent state you now have. You are probably aware that Linux networking--unlike UNIX networking--is a God-awful mess. That's because every self-styled "genius" has contributed freely to Linux. This is one reason why, for example, there are umpteen half-baked interfaces to the kernel function that opens a file--whereas there used to be ONE. So-called "software engineers" characterize this as "improvement."
You get what you pay for. This diatribe isn't a fix, it's just a reality check. Most Linux aficionados spend untold time tearing their hair out. I don't see this with commercial UNIXes, such as MacOS.
Tell me what service you are endeavoring to contact OR host and what ports are open.
Also, do you have a listener on that port? /etc/inetd.conf (or whatever sixty-nine files SuSE has split that into as an "improvement") must be configured so that inetd knows to listen for incoming requests on such-and-such TCP or UDP port and, when each one is accepted, spawn such-and-such demon to handle it, either iteratively or concurrently as directed.
"... remotely ... lost connection"
You remind me of my friend who went into business hosting payphones all over this and that airport and hotel. Now and then, a certain phone simply would not answer, which was a clear sign that local miscreants had put a firecracker in the coin return and detonated it for kicks.
Not sure WHY I was so reminded, but it's a cute story anyway . . .