Implement SO_REUSEPORT

[terrypacker]

From a comment on this commit cfd52615fa3bfb93ce8150ecbaa8ec81323960c9

How about reusePort to (hopefully) allow multiple instances to use the same interface?

SO_REUSEPORT is what most people would expect SO_REUSEADDR to be. Basically, SO_REUSEPORT allows you to bind an arbitrary number of sockets to exactly the same source address and port as long as all prior bound sockets also had SO_REUSEPORT set before they were bound.

More info here

[mlohbihler]

Java only has setReuseAddress AFAICS. What is the proposal here? To change the name of the field/method?

[Frozenlock]

Looks like you are right... for now. SO_REUSEPORT should be present in Java 9.

[Frozenlock]

Now that Java 9 is out, I'd like to bring back the attention on this issue. :-)

(Hopefully this simple change would allow multiple instances of BACnet4J to run on a single IP/port)

[Frozenlock]

This appears to have been added, so this issue can probably be closed.

A side question : is it possible to have multiple Bacnet devices using the same IP and communicate normally between them? I've given it a quick try, but all the devices on the same IP are answering the readProperty requests at the same time, even if they are the one that sent the request..

[terrypacker]

@Frozenlock I'm going to close this but I wrote a test awhile back so here is a starting point if you want:

/**
 * Copyright (C) 2018  Infinite Automation Software. All rights reserved.
 */
package com.infiniteautomation.bacnet4j.npdu.ip;

import java.net.InterfaceAddress;
import java.util.List;

import org.junit.Assume;
import org.junit.Test;

import com.serotonin.bacnet4j.LocalDevice;
import com.serotonin.bacnet4j.npdu.ip.IpNetwork;
import com.serotonin.bacnet4j.npdu.ip.IpNetworkBuilder;
import com.serotonin.bacnet4j.transport.DefaultTransport;
import com.serotonin.bacnet4j.transport.Transport;

/**
 * @author Terry Packer
 *
 */
public class MulltipleLocalDevices {

    @Test
    public void testMultipleLocalDevices() throws Exception {

        List<InterfaceAddress> usable = BacnetIpUtils.listUsableBACnetInterfaces();
        Assume.assumeTrue(usable.size() > 0);

        InterfaceAddress address = usable.get(0);
        String bindAddress = address.getAddress().toString().split("/")[1];
        String broadcastAddress = address.getBroadcast().toString().split("/")[1];

        //Configure the first network, ensure we set reuse address
        IpNetwork networkOne = new IpNetworkBuilder()
                .withLocalBindAddress(bindAddress)
                .withBroadcast(broadcastAddress, address.getNetworkPrefixLength())
                .withLocalNetworkNumber(1).withPort(9000).withReuseAddress(true).build();
        Transport transportOne = new DefaultTransport(networkOne);
        LocalDevice localDeviceOne = new LocalDevice(1, transportOne);

        IpNetwork networkTwo = new IpNetworkBuilder()
                .withLocalBindAddress(bindAddress)
                .withBroadcast(broadcastAddress, address.getNetworkPrefixLength())
                .withLocalNetworkNumber(1).withPort(9000).withReuseAddress(true).build();
        Transport transportTwo = new DefaultTransport(networkTwo);
        LocalDevice localDeviceTwo = new LocalDevice(2, transportTwo);

        localDeviceOne.initialize();
        localDeviceTwo.initialize();

    }

}