Login to your router and locate the UPnP setting. Go to WAN then on the basic config, click yes for Enable UPnP. See screenshot below.
Next, get this script from github. See command line below which I have experience myself.
user@localhost:~$ wget https://raw.githubusercontent.com/gryphius/port-forward/master/port-forward.py --2015-09-04 02:53:28-- https://raw.githubusercontent.com/gryphius/port-forward/master/port-forward.py Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 22.214.171.124 Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|126.96.36.199|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 9115 (8.9K) [text/plain] Saving to: ‘port-forward.py’ port-forward.py 100%[=======================================================================================================>] 8.90K --.-KB/s in 0s 2015-09-04 02:53:29 (46.3 MB/s) - ‘port-forward.py’ saved [9115/9115] user@localhost:~$ chmod 755 port-forward.py user@localhost:~$ ./port-forward.py Found 1 UPnP routers: 192.168.133.1:42917 No external port specified. user@localhost:~$ ./port-forward.py -e 1337 -v -r 192.168.133.1 -l 9999 -d 'forward 1337 to 9999' Discovering routers... Found 1 UPnP routers: 192.168.133.1:42917 port forward on 192.168.133.1 successful, 1337->192.168.133.20:9999 user@localhost:~$ nc -l 9999 user@localhost:~$
As you can read above, the script is downloaded and then permission is set accordingly. Noticed that UPnP is found on my router on port 42917. Then you can instruct the router to port forward, in this example port 1337 to an internal of this machine. In this example, my local ip is 192.168.133.1 and the application is running on port 9999. Now, to simulate this work, you can use command nc to listen on port 9999.
To test if this work, just get your public ip and telnet to your router on port 1337, your router should forward this traffic to internal machine 188.8.131.52 port 9999. As you can also see above, when telnet is done, nc port listen is also closed. That's it. Have fun port forwarding!