DeleGate with a SERVER=tcprelay parameter
relays communication between a client and a server
on a single TCP connection
without interpreting what is transmitted on it.
Thus an arbitrary application protocol on TCP,
even if it is not in supported protocol list of DeleGate,
can be relayed by SERVER=tcprelay.
But value added services, including caching, mounting and logging,
are not available in this case.
Connecting to arbitrary destination servers depending on a request from
a client is not possible.
Application protocols which dynamically create other connections besides
the main connection, like FTP, are not relayable.
Application protocols which exchange some kind of name depends on
an origin server on the protocol, like a full URL in HTTP,
are not relayable too.