java.net.BindException: Cannot assign requested address

Question

I want to use low port in my application (SNMP Trap Receiver on Spring web + Tomcat7). As I told in this thread Binding Low Port to Java Program on Ubuntu Server, 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.

I check if the port has used, I see that the port still free. I check my /etc/host content, it is like this:

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

note: my OS is ubuntu server

Answer 1

You should bind to 0.0.0.0 instead of trying to specify a local-address.