How DDP works in Meteor

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