I am using netcat on some Linux machines (see this other question), but seeing some unexpected behavior.
Unlike the guide in the accepted answer, I am not using UDP tunneling to do DNS queries. I have a remote server that I can log into, but not install software on, and I'm trying to tunnel UDP traffic from my computer to the server, and then setup a separate tunnel to send UDP responses back from the server to my machine.
The tunnel going from my machine to the server is working perfectly, however on the server side, the instance of netcat that is listening for the response from the UDP server will close the listener after receiving the first response. So I can send a request and get 1 response back, but any subsequent requests make it to the server okay but responses are not received. Using netstat I can see that before the response is received netcat is listening, but the port is then closed after the response is received.
The netcat instance on my machine seems to handle everything just fine. Both machines are running netcat v1.10-38. Any ideas what is going on?