Your Delphi TServerSocket component probably binds to INADDR_ANY, and thus listens on all available interfaces. This would make it APPEAR you're able to connect to
localhost and others are able to connect to your
IP, but in reality if you bound strictly to '127.0.0.1', people would not be able to make a connection to your computer from over the Internet.
struct sockaddr_in addr;
addr.sin_addr.s_addr = INADDR_ANY; // bind to all interfaces
as opposed to
addr.sin_addr.s_addr = inet_addr("127.0.0.1"); // bind to 127.0.0.1
or
addr.sin_addr.s_addr = inet_addr("69.29.23.12"); // bind to that
IP (provided it's assigned to your computer) and now people can connect on it