org.zeromq.ZMQException: Errno 48 : Address already in use - zeromq

Question

I am trying to implement a pub-sub example using ZeroMQ.
I run the publisher's code in a docker container and the subscriber's code in another one.
My subscriber is:
private ZMQ.Context context;
{
context = ZMQ.context(1);
}
public void receive() {
System.out.println("Getting subscriber, listening to tcp://localhost:5565");
getSubscriber();
byte[] raw;
System.out.println("Watching for new Event messages...");
try {
while (!Thread.currentThread().isInterrupted()) {
raw = subscriber.recv();
System.out.println("Event received " + raw);
}
} catch (Exception e) {
System.out.println("Unable to receive messages via ZMQ: " + e.getMessage());
}
if (subscriber != null)
subscriber.close();
subscriber = null;
System.out.println("Attempting restart of Event message watch.");
receive();
}
private ZMQ.Socket getSubscriber() {
if (subscriber == null) {
try {
subscriber = context.socket(ZMQ.SUB);
subscriber.connect("tcp://localhost:5565");
subscriber.subscribe("".getBytes());
} catch (Exception e) {
System.out.println("Unable to get a ZMQ subscriber. Error: " + e);
subscriber = null;
}
}
return subscriber;
}
And my publisher is:
private ZMQ.Context context;
{
context = ZMQ.context(1);
}
public synchronized void sendEventMessage(Event event) {
try {
if (publisher == null) {
getPublisher();
}
if (publisher != null) {
publisher.send(event);
}
} catch (Exception e) {
System.out.println("Unable to send message via ZMQ");
}
}
private void getPublisher() {
try {
if (publisher == null) {
publisher = context.socket(ZMQ.PUB);
publisher.bind("tcp://192.168.32.9:5565"); //where 192.168.32.9 is the IP of the subscriber's docker container
Thread.sleep(PUB_UP_SLEEP); // allow subscribers to connect
}
} catch (Exception e) {
System.out.println("Unable to get a publisher. Error: " + e);
publisher = null;
}
}
When I start the application, I register a subscriber and the logs are:
[2018-12-10 08:01:02.138] boot - 1 INFO [main] --- ZeroMQEventSubscriber: Getting subscriber, listening to tcp://localhost:5565
[2018-12-10 08:01:02.249] boot - 1 INFO [main] --- ZeroMQEventSubscriber: Watching for new Event messages...
My problem is that when I invoke sendEventMessage, the subscriber does not receive anything and on the publisher I get this error:
[2018-12-10 08:54:16.388] boot - 1 ERROR [task-scheduler-5] --- ZeroMQEventPublisherImpl: Unable to get a publisher. Error: org.zeromq.ZMQException: Errno 48 : Address already in use
Any ideas why I cannot bind to the address where the subscriber has connected?