DCC2 Protocol for IRC file transfers

Joe_Hypnol writes "I just noticed this bit of news over at IRC Junkie. Looks like a bunch of irc client authors (and even more) are putting their heads together to come up with DCC2, a replacement for the the poorly designed DCC IRC file transfer specification. The old protocol was basically based on a usenet post, but this new one is looking like it'll be a full-blown standard. It's currently an IETF internet working draft. Read the press release at DCC2.org."

Comments

Re:PIrates rejoice

[Tiberius_Fel]

I seriously use DCC for things other than pirating. DCC is commonly used by my particular group to pass along logs, interesting documents, proposals & updates, et cetera. In a sense you might say it's like P2P - it's used by a lot of filesharers / pirates - but it's not the exclusive domain of those types.

DCC isn't so good but

[Rosco P. Coltrane]

It's easy to dismiss DCC as a flawed protocol. Sure it has its shortcomings, but remember, it was designed before the internet started to become firewalled to death. I remember, until perhaps 1997, DCC was just fine and easy to use, and almost never gave us any trouble. Now you have to prep up your firewall, deal with your NAT box, or get the IRC client to take care of it, ...

Here's a quick overview of how a DCC connection is initiated:

- The initiator's IRC client opens a TCP socket, then (let's call him Bob) sends a DCC (CHAT, SEND) request through normal messaging. Basically it's a plain-text message starting with ^A, similar to a CTCP request. Then it listens to the socket.

- The target IRC client (let's call him Joe) gets it, decodes Bob's socket's IP address and port inside the DCC request, and tries to initiate a TCP connection to Bob.

- Once the connection is established, if it's a DCC CHAT, text is sent as-is across the TCP connection back and forth. If it's a DCC SEND, then the file transfer protocol is used over the connection.

Of course, the confusing thing for people who aren't familiar with DCC is that it's the initiator's client that temporarily becomes the server for the contacted client, and not the other way round, like most people are used to, with http for example. So basically, it's people who initiate DCC connections who must open one or more inbound TCP ports in their firewalls, and configure their IRC clients to limit themselves to using those ports.

Re:What's the difference?

[hey]

RTFA...

The current DCC protocol does not address IPv4 vs. IPv6 issues, SSL/
TLS encryption negotiation, NAT and Firewall traversal, or multiple
file/directory file transfers....

Re:I've got an idea

[undertow3886]

You can get a program called scponly (works with sftp too) and set that as your guest user's shell. It makes it so they can use sftp, but not log on with plain ssh and get a console. It works great for me.