Deprecated, use https://github.com/wangyuntao/portal instead.
Expose local servers behind NAT or firewall to the Internet
On a publicly accessible machine, run:
./duck -l -addr :9990 -p test_password
On the machine where your local servers are running, run:
./duck -addr DUCK_SERVER_IP:9990 -p test_password <local server port> <local server port> ...
Now you can connect to the public duck server and the tcp traffic will be forwarded to your specific local server according to the port.