Test connectivity through netcat

You want to test that networking is properly configured before you actually run eny services. For example you are migrating from mod_jk to mod_proxy so your DMZ should be able to connect to tomcat on port 8443 (HTTPS) instead of 8009 (AJP). You cannot make any changes so far but it is Friday and you want to make sure the routes through DMZ firewalls are working correctly. Just put a listener in the tomcat server and use a client to connect to it from Apache. So in tomcat:

$ nc -l 8443

In Apache use a client:

$ nc tomcatServerDomainOrIp 8443
Hello

And you should get what you type (Hello) in the server side if the connectivity is correct. This is of course testing TCP traffic on port 8443.