With the current client it is impossible to start mulitple instances of bitcoin on one system, as they compete for the listen port. This patch adds a command line option to not accept bitcoin connection from outside.
This can be useful in some cases:
- Testing e-commerce software on the testnet with multiple clients on one machine (akin to paypal sandbox testing)
- When multiple users on one shared server want to run the bitcoin client
- As a primitive security measure
Of course it would be even better to specify a port to listen on on the command line, but as I understood the current protocol has no support for alternative ports, so this would be useless at this stage.