title: java.net.BindException: Cannot assign requested address
body: <p>I want to use low port in my application (SNMP Trap Receiver on Spring web + Tomcat7). As I told in this thread <a href="https://stackoverflow.com/questions/30568335/binding-low-port-to-java-program-on-ubuntu-server?noredirect=1#comment49213056_30568335">Binding Low Port to Java Program on Ubuntu Server</a>, before, I got error Permission denied. Then I change tomcat7 user group be root. But after that, I got java.net.BindException: Cannot assign requested address error. For every port that I try (low or high port), I always got this error.</p>
  
  <p>I check if the port has used, I see that the port still free.
  I check my /etc/host content, it is like this:</p>
  
  <pre><code>127.0.0.1 localhost 
  127.0.1.1 test-server 
  # The following lines are desirable for IPv6 capable hosts 
  ::1 localhost ip6-localhost ip6-loopback 
  ff02::1 ip6-allnodes 
  ff02::2 ip6-allrouters 
  124.81.xx.x test-server.com
  </code></pre>
  
  <p>note: my OS is ubuntu server</p>