DCC Resume Protocol

The current protocol is very simple.

User1 is sending the file.

User2 is receiving the file.

To initiate a DCC Send, User1 sends:

PRIVMSG User2 :DCC SEND filename ipaddress port filesize

Normally, if User2 accepts the DCC Send request, User2 connects to the address and port number given by User1 and the file transfer begins.

If User2 chooses to resume a file transfer of an existing file, the following negotiation takes place:

User2 sends:

PRIVMSG User1 :DCC RESUME filename port position

filename = the filename sent by User1.

port = the port number sent by User1.

position = the current size of the file that User2 has.

User1 then responds:

PRIVMSG User2 :DCC ACCEPT filename port position

This is simply replying with the same information that User2 sent as acknowledgement.

At this point User2 connects to User1 address and port and the transfer begins from the specified position.

Note: The newer versions of mIRC actually ignore the filename as it is redundant since the port uniquely identifies the connection. However, to remain compatible with older mIRC's, mIRC still sends a filename as file.ext in both RESUME and ACCEPT.