I'm able to connect to my xenserver using virsh like so and I see the VMs. 

[jdrews@flynx ~]$ virsh -c xenapi://root@192.168.1.23?no_verify=1 list
Enter root's password for 192.168.1.23
 Id    Name                           State
----------------------------------------------------
Struct did not contain expected field memory_overhead.
Struct did not contain expected field snapshot_info.
Struct did not contain expected field snapshot_metadata.
Struct did not contain expected field parent.
Struct did not contain expected field children.
Struct did not contain expected field bios_strings.
Struct did not contain expected field protection_policy.
Struct did not contain expected field is_snapshot_from_vmpp.
Struct did not contain expected field appliance.
Struct did not contain expected field start_delay.
Struct did not contain expected field shutdown_delay.
Struct did not contain expected field order.
Struct did not contain expected field VGPUs.
Struct did not contain expected field attached_PCIs.
Struct did not contain expected field suspend_SR.
Struct did not contain expected field version.
 0     Control domain on host: xenserver-4 running
Struct did not contain expected field memory_overhead.
Struct did not contain expected field snapshot_info.
Struct did not contain expected field snapshot_metadata.
Struct did not contain expected field parent.
Struct did not contain expected field children.
Struct did not contain expected field bios_strings.
Struct did not contain expected field protection_policy.
Struct did not contain expected field is_snapshot_from_vmpp.
Struct did not contain expected field appliance.
Struct did not contain expected field start_delay.
Struct did not contain expected field shutdown_delay.
Struct did not contain expected field order.
Struct did not contain expected field VGPUs.
Struct did not contain expected field attached_PCIs.
Struct did not contain expected field suspend_SR.
Struct did not contain expected field version.
 23    VM1 (RH5.2 10.4.1.69 eth0) running
Struct did not contain expected field memory_overhead.
Struct did not contain expected field snapshot_info.
Struct did not contain expected field snapshot_metadata.
Struct did not contain expected field parent.
Struct did not contain expected field children.
Struct did not contain expected field bios_strings.
Struct did not contain expected field protection_policy.
Struct did not contain expected field is_snapshot_from_vmpp.
Struct did not contain expected field appliance.
Struct did not contain expected field start_delay.
Struct did not contain expected field shutdown_delay.
Struct did not contain expected field order.
Struct did not contain expected field VGPUs.
Struct did not contain expected field attached_PCIs.
Struct did not contain expected field suspend_SR.
Struct did not contain expected field version.
 25    DeviceSimulator (192.168.1.150) running
Struct did not contain expected field memory_overhead.
Struct did not contain expected field snapshot_info.
Struct did not contain expected field snapshot_metadata.
Struct did not contain expected field parent.
Struct did not contain expected field children.
Struct did not contain expected field bios_strings.
Struct did not contain expected field protection_policy.
Struct did not contain expected field is_snapshot_from_vmpp.
Struct did not contain expected field appliance.
Struct did not contain expected field start_delay.
Struct did not contain expected field shutdown_delay.
Struct did not contain expected field order.
Struct did not contain expected field VGPUs.
Struct did not contain expected field attached_PCIs.
Struct did not contain expected field suspend_SR.
Struct did not contain expected field version.
 28    VM3 (RH 5.2 10.4.1.15 eth0) running
Struct did not contain expected field memory_overhead.
Struct did not contain expected field snapshot_info.
Struct did not contain expected field snapshot_metadata.
Struct did not contain expected field parent.
Struct did not contain expected field children.
Struct did not contain expected field bios_strings.
Struct did not contain expected field protection_policy.
Struct did not contain expected field is_snapshot_from_vmpp.
Struct did not contain expected field appliance.
Struct did not contain expected field start_delay.
Struct did not contain expected field shutdown_delay.
Struct did not contain expected field order.
Struct did not contain expected field VGPUs.
Struct did not contain expected field attached_PCIs.
Struct did not contain expected field suspend_SR.
Struct did not contain expected field version.
 30    Router 10.4.1.x (192.168.1.254) running

I'm using a compiled version of libvirt that I enabled the xenapi protocol. 

[jdrews@flynx ~]$ virsh -v
0.9.10

I can also start and stop VMs via virsh.

So the next move for me was to get this working with the java bindings, libvirt-java. I grabbed libvirt-0.4.7.jar and built it. Eclipse is set up and I can see everything correctly. I built a small runnable test jar and ran it. 

[jdrews@flynx ~]$ java -jar VirtAPITesting.jar 
connecting on: xenapi://root@192.168.1.23?no_verify=1
Enter root's password for 192.168.1.23
WARNING: THE ENTERED PASSWORD WILL NOT BE MASKED!
mytestpass
exception caught:org.libvirt.LibvirtException: unable to connect to server at '192.168.1.23:16514': No route to host
level:VIR_ERR_ERROR
code:VIR_ERR_SYSTEM_ERROR
domain:VIR_FROM_RPC
hasConn:false
hasDom:false
hasNet:false
message:unable to connect to server at '192.168.1.23:16514': No route to host
str1:%s
str2:unable to connect to server at '192.168.1.23:16514': No route to host
str3:null
int1:-1
int2:-1

Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: java.lang.NullPointerException
at com.codemettle.VirtAPI.testing.VirtAPITesting.main(VirtAPITesting.java:29)
... 5 more

But I know there is a route to the host as virsh could get there. Sanity check: ping works fine too. 
[jdrews@flynx ~]$ ping 192.168.1.23
PING 192.168.1.23 (192.168.1.23) 56(84) bytes of data.
64 bytes from 192.168.1.23: icmp_req=1 ttl=64 time=1.58 ms

Here is the code I'm running in the VirtAPITesting.jar. For the most part it's a direct copy of the example at the end of the libvirt java page: http://libvirt.org/java.html

package com.jdrews.VirtAPI.testing;
import org.libvirt.*;

public class VirtAPITesting {
    public static void main(String[] args) throws InterruptedException {
    System.setProperty("jna.library.path", "/usr/local/lib/");
        Connect conn=null;
        System.out.println(
        ConnectAuth defaultAuth = new ConnectAuthDefault();
        try{
            conn = new Connect("xenapi://root@192.168.1.23?no_verify=1", defaultAuth, 0);
        } catch (LibvirtException e){
            System.out.println("exception caught:"+e);
            System.out.println(e.getError());
        }
        
        try {
            Domain testDomain=conn.domainLookupByName("DeviceSimulator (192.168.1.150)");
            System.out.println("Domain:" + testDomain.getName() + " id " +
                               testDomain.getID() + " running " +
                               testDomain.getOSType());
        } catch (LibvirtException e) {
            System.out.println("exception caught:"+e);
            System.out.println(e.getError());
        }
        
    }
}

Does anyone know what's going on here? Any help or advice would be greatly appreciated. Thanks!

--
Jon Drews
jondrews.com