App running in Docker on EB refuses connecting to self - amazon-web-services

Question

I have a Play 2 web application, which I deploy to Elastic Beanstalk using Docker. In this web app, I start an Akka cluster. The starting procedure involves adding all nodes in the autoscaling group as seed nodes (including itself). On the first deploy to EB I specify to deploy to a VPC (I only select one availability zone).
When I run the app and start the cluster, I get the following message:
AssociationError [akka.tcp://cluster#localhost:2551] -> [akka.tcp://cluster#172.31.13.25:2551]: Error [Invalid address: akka.tcp://cluster#172.31.13.25:2551] [
akka.remote.InvalidAssociation: Invalid address: akka.tcp://cluster#172.31.13.25:2551
Caused by: akka.remote.transport.Transport$InvalidAssociationException: Connection refused: /172.31.13.25:2551
Where 172.31.13.25 is the IP of the EC2 instance, and 2551 is the port.
In my Dockerfile I have "EXPOSE 9000 2551". In the EC2 Security Group I have enabled all inbound traffic to
0.0.0.0/0 (and all outbound traffic). In the VPC Network ACLs (and security groups) I've also opened for all traffic.
This is my Dockerfile
FROM dockerfile/java:latest
MAINTAINER a <a#b.de>
EXPOSE 9000 2551
ADD files /
WORKDIR /opt/docker
RUN ["chown", "-R", "daemon", "."]
USER daemon
ENTRYPOINT ["bin/myapp"]
CMD []
Why does my EC2 instance refuse a connection to itself on port 2551?

Answer 1

Turns out this is not possible as of now using Docker on Elastic Beanstalk.
It is, however, possible using Tomcat.
Using play/activator, you can deploy a WAR file. By injecting the following .ebextensions config file into the war file, I was able to get an extra port open between the EC2 instances:
Resources:
ExtraPortsSGIngress:
Type: AWS::EC2::SecurityGroupIngress
Properties:
GroupId: { "Ref" : "AWSEBSecurityGroup" }
IpProtocol: "tcp"
FromPort: "2551"
ToPort: "2551"
SourceSecurityGroupId: { "Ref" : "AWSEBSecurityGroup" }