This document describes the Distributed Data Protocol (DDP) used by Meteor to manage data and remote procedure calls between a client and server. It discusses DDP connection establishment, ping/pong messages, calling remote methods, and managing subscriptions and data transmission with message types like added, removed, and ready. Tools for analyzing DDP traffic and libraries for building DDP clients in various languages are also mentioned.

1. DDP
Michael Lazarski
twitter: lazarskiDOTme

2. Distributed Data Protocol.
- Stateful websocket protocol
- Connection between the Server and Client
- Handles Remote Procedure Calls (RPC)
- Manages data
- Meteor uses Version “1” (pre 1.0.0 used
“pre2” or “pre1”

3. Client to Server Connection
Client sends “connect” msg:
{"msg":"connect","version":"1","support":["1","
pre2","pre1"]}
Server sends “connected” msg:
{"msg":"connected","session":"
KXKTWoDXK2n4osF79"}

4. Ping to the Pong
Client sends {"msg":"ping"}
Server sends {"msg":"pong"}
or
Server sends {"msg":"ping"}
Client sends {"msg":"pong"}
In meteor usally the Server sends the ping

5. Remote Procedure Calls
Client sends: {"msg":"method","method":"methodName","
params":[Params values],"id":"messageId"}
Server sends: {"msg":"result","id":"messageId","result":
SomeResult}
Server sends: {"msg":"updated","methods":["messageId"]}

6. Managing Data
msg types:
- sub: Subscribe to a Collection
- unsub: Unsubscribe from a Collection
- nosub: Subscriben is not allowed by the server
- added: A document was added to local set
- changed: A document in the local set has a new value
- removed: A document was removed
- ready: Initial send of data is finished
- addedBefore: like added but in ordered collection with the document Id
after the document added
- moveBefore: if a ordered collection has changed

7. Example sub
Client Sends:
{"msg":"sub","id":"RandomSeed","name":"
PublicationName","params":[SomeParams]}
Server Sends: {"msg":"added","collection":"
collectionName","id":"DocumentId","fields":
{DocumentFields}}
Server Sends: {"msg":"ready","subs":["randomSeed"]}

8. Demo Time

9. DDP Analyzer
A DDP Proxy for dumping the ddp message to a console
install: sudo npm install -g ddp-analyzer
start: ddp-analyzer-proxy
start meteor:
export DDP_DEFAULT_CONNECTION_URL=http://localhost:3030
meteor
Github: https://github.com/arunoda/meteor-ddp-analyzer

10. DDP Clients
There are DDP Clients for:
Node.JS, Android, Java, Python, Ruby,
Objective C, .net, GO, Dart ….
Quelle: http://meteorpedia.com/read/DDP_Clients

11. Install: npm install ddp
github:https://github.com/mondora/ddp.js
node.js ddp client