Cannot connect from local machine to TCP server on AWS EC2 (Ubuntu) - amazon-ec2

Question

I've coded up a basic TCP server/client, taking code from the first example on https://docs.python.org/3/library/socket.html#example
# Echo server program
import socket
HOST = '' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
with conn:
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
# Echo client program
import socket
HOST = '1.2.3.4' # The remote host (I change this with my box's IP)
PORT = 50007 # The same port as used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
data = s.recv(1024)
print('Received', repr(data))
NOTE: I'm using my actual EC2 IP not 1.2.3.4
If I run the client on my local machine and the server on a remote box (hosted by vultr) it works.
But if host the server on an AWS EC2 instance, it doesn't.
I've gone into the Security Group for the EC2 instance, and added inbound+outbound "Custom TCP+UDP" rules. I've tried allowing the specific port the server is using, as well as putting 0-65535.
If I run a client on the same EC2 instance, that works.
I can't think what else to try.
Is anyone able to get this working on EC2?

Answer 1

I was using my AMI's private IP (which I use to ssh into the box).
I needed to use the PUBLIC IP.
It seems on vultr they are the same, which is why it worked.