Stone is an application layer TCP/IP packet repeater. It repeats TCP and UDP packets from the inside of a firewall to the outside or vice versa. It is simple, supports OpenSSL for encrypting and decrypting packets, performing client and server verifications, and sending a substring of the subject of the certificate to the destination, can operate as an HTTP proxy, and performs POP to APOP conversion. It also supports IPv6 and can convert between IPv4 and IPv6 each other.