What IP to use for self-testing?

Question

A bunch of servers offer functionality on a particular port (the port listens on all interfaces). Servers must self-test their own functionality by connecting to themselves. What DNS name or IP should the test connection use?

Ideally, I'd use one of the local IPs and be done with it (e.g. '192.13.1.5'). However, obtaining the list of local IPs is difficult for the test code.

I can use 'localhost' (127.0.0.1), but this uses the loopback interface and bypasses network hardware. Which leads me to...

Question: Is there shorthand notation for "Any local IP this server uses"? (except loopback address).

Using '0.0.0.0' seems to work on Linux, but not on Windows.

Answer 1

To add to Michael Hampton's suggestion, Windows should recognize %computername% as an environment variable, which you can ping, etc.

It looks to me like the PowerShell cmdlet Test-NetConnection along with the windows environment variable might do what you want. You can specify a port, but since you didn't mention one I just used

Test-NetConnection -ComputerName $env:COMPUTERNAME

and that worked fine on my laptop. The port syntax for checking port 135 (as a random example) would be

Test-NetConnection -Port 135 -ComputerName $env:COMPUTERNAME

Answer 2

Thanks folks - deeply appreciate your help here. Yes, hostname environment variables would work but require code to access. I'm with Shane - 0.0.0.0 should work, but there's something tricky about it.

I figured I'd need to create code (which had to be Java) so I wrote this to obtain three sets of IPs:

    List<String> IPAddress = new ArrayList<String>();
    List<String> NonLoopbackIPv4Address = new ArrayList<String>();
    List<String> NonLoopbackIPv6Address = new ArrayList<String>();

    try {
        Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces();
        while(en.hasMoreElements()){
            NetworkInterface ni=(NetworkInterface) en.nextElement();
            Enumeration<InetAddress> ea = ni.getInetAddresses();
            while(ea.hasMoreElements()) {
                InetAddress ia= (InetAddress) ea.nextElement();

                //Add entries to the overall address array 
                IPAddress.add(ia.getHostAddress());

                //Add entries to non-loopback IPv4 address array
                if (!ia.isLoopbackAddress() && (ia.getClass() == Inet4Address.class))  {
                    NonLoopbackIPv4Address.add(ia.getHostAddress());
                }

                //Add entries to non-loopback IPv6 address array
                if (!ia.isLoopbackAddress() && (ia.getClass() == Inet6Address.class))  {
                    NonLoopbackIPv6Address.add(ia.getHostAddress());
                }
            }
         }
    } catch (Exception e) {
        //catch and process necessary exceptions, etc...
        throw new Exception (e);
    }

...where:

• IPAddress - list of all IP addresses for this host (both v4 and v6), including those bound to the loopback interface
• NonLoopbackIPv4Address - list of all IPv4 addresses for this host, excluding those bound to the loopback interface
• NonLoopbackIPv6Address - list of all IPv6 addresses for this host, excluding those bound to the loopback interface