1. N

    UDP 53

    Hello, I have a small issue. I have a virtual server with Ubuntu Server 20.04.6, and I've installed a DNS server on it. However, it doesn't respond on UDP port 53. It only responds if I use the command "dig @109.XXX.3.X thenarbox.com +vc." Of course, I'm running the command from a different...
  2. U

    Socket hangs in recv randomly

    Hi, I have set up a network with a Linux host communicating over TCP/IP with a standard Windows computer. There is a strange behavior occurring sporadically and maybe you have an idea where this might come from. On Linux side there has been a standard TCP socket created which listens for an...
  3. Rob

    How to test open UDP ports

    You've opened a UDP port on your server but not sure how to check if you can reach it from the outside. When testing TCP ports, you can check with tools like nmap or nc only from the outside, but the nature of UDP is that it doesn't send anything back so you need to monitor the port on the...
  4. J

    UDP listen on the secondary interface

    Hi, I want to listen to UDP packets on the secondary interface (my own program, but this is reproducible with netcat as well). I have an ubuntu 16.04.02 LTS system, with 2 different network interfaces: ethernet - 10.x.x.x wifi - 192.168.x.x The routing table is the default one...