I have a server running UDP server on port 50000. This server receives updates from clients, and pings back the clients every 5 seconds to the socket they were connected from.
Now I want to redirect all the traffic to and from this UDP server via another server. Basically I want to setup a transparent proxy in front of this server. The reason is that I want to be able to easily control which server handles the UDP traffic, without the need to change DNS settings.
At first I tried usingn socat to create this proxy:
socat UDP-LISTEN:50000,fork UDP:myserver:50000
But this seems to work well for incoming traffic, but back traffic from my server to the clients doesn't reach its destination. Also it seems that socat forks another process for each connection, so I might end up with too many processes and also dead processes when clients disconnect/switch IP.
I realized that I can use iptables NAT functionality for this, but it doesn't seem to work for me. The configuration I've tried is:
sudo iptables -t nat -A PREROUTING -p udp --dport 50000 -j DNAT --to-destination myserver:50000
But it doesn't seem to work -- I don't even see the connections on my server. I'm not sure if it's due to wrong configuration or due to some other issues.
- Do I need to somehow restart iptables once I add the nat configuration?
- Do I need to allow traffic to the incoming port or having the NAT setting is enough?
UPDATE: The server that actually handles the traffic is on a different machine than the one that I'm trying to setup iptables on.