schmichael/gist:7034672

## gistfile1.md

      
    Raw
  

              gistfile1.md
            
          
    Original gist: https://gist.github.com/schmichael/7034672
Whispering Gophers

See: http://whispering-gophers.appspot.com/talk.slide#1 via
{
    "ID": "<unique string>",
    "Addr": "<IP:Port of sender>",
    "Body": "<the actual message to display>"
}
Basic protocol:

Manually connect to at least 1 peer; connect to new peers seen in Addr fields
Accept connections from any peer
Broadcast all messages to all peers (except Addr); store list of Seen messages by ID to avoid rebroadcasting
Output non-local messages to stdout; send messages from stdin
Payloads without a Body and/or with unknown keys should be silently ignored to support extensions

Stretch goals:
Roughly ordered based on difficulty.

Drop old messages - requires Timestamp field
Forget old messages (the basic daemon slowly uses all memory) - may use Timestamp field - see below
Base ID on hash of Addr + Body + Timestamp - see below
Discover based on UDP broadcasts See below
Build web interface into daemon
Simple input form (textbox + submit button)
Chat output (refreshed on a timer or using websockets if you're really fancy)
Peer connection controls (connect to a new host, disconnect from a host)
File transfers - see below
Send backlog to newly connected peers - see backlog below
Flood control: Disconnect and blacklist peers whose activity exceeds a threshold
PKI all the things
Scalable routing

UDP Broadcast Protocol
Broadcasts should be of the form: ":" and may be sent on behalf of any peers.
Timestamp field
To support various features, messages should include an optional Timestamp field of the format milliseconds since UNIX epoch as a number. For example:
{
    "ID": "abc123",
    "Addr": "192.168.1.53:2345",
    "Body": "Hello world!",
    "Timestamp": 1382050782085
}
Hashed ID field
To support very rudimentary payload verification, use a hash of the concatenated Addr, Body, and Timestamp fields. To allow backward compatibility with old clients, hashed IDs should be of the form:
{
    "ID": "hash:sha256:<hash>",
    ...
}
Where each string starts with "hash:" followed by the name of the hash function used, followed by a colon and the hex encoded hash.
Unknown hash functions should cause the reader to revert to the basic random-string-ID behavior.
Peers should drop messages whose hashes don't match the current message payload.
File transfers
Two new keys: "FileType" and "FileContents"

FileType should be the MIME type like: "image/gif"
FileContents should be the Base64 encoded file contents

Backlog
Upon receiving a new connection from a peer, a daemon should replay that peer the last N messages (the actual number shouldn't be important) to the peer.
Next?


Make protocol newline delimited. Golang's Decoder makes it quick and easy to get up and running quickly, but it also makes lots of common error cases impossible to handle. Breaking change.
Define whether Addrs (the sender's address) should be ephemeral or persistent. Seemed like most implementations had ephemeral conenctions for sending which breaks the peer autodetection.
Gavin's UDP broadcast feature is another fix for this, but ephemeral clients are still troublesome.
Polyglot hack night?