Btw - question to Stefan as the JavaScript guru - what do you consider the standard/defacto-standard/right/best-practice way of doing S->C json-rpc, what (javascript) library do you use for this?

As for an explicitly standard way, there is none. The JSON-RPC 1.0 spec says "The specifications do not require a certain transport protocol. The use of TCP/IP socket streams is encouraged. The serialized request and response objects are sent to the peers through the byte streams. " The JSON-RPC 2.0 spec goes out of its way to say "It is transport agnostic in that the concepts can be used within the same process, over sockets, over http, or in many various message passing environments."

The de-facto standard for bidirectional JSON-RPC is plain TCP sockets. BitcoinJS currently implements this - we detect whether an incoming connection is HTTP or raw JSON-RPC based on the first character. (HTTP must start with an uppercase letter, raw JSON-RPC must start with an opening curly bracket.)

There are two things to watch out for with JSON-RPC over plain TCP:

1. Plain TCP sockets (unlike HTTP) have no standardized authentication mechanism, so I added an extra RPC call auth("username", "password").

2. The TCP packets may or may not correspond to JSON-RPC messages. You can either use a streaming JSON parser (yajl in ANSI C, Jackson in Java, etc.), or you can just count (non-string-literal) curly braces to detect when a complete message has arrived.

Many JSON-RPC libraries come with TCP socket support out of the box: http://json-rpc.org/wiki/implementations

We're planning to add more features to our JSON-RPC API in the future, such as:

- JSON-RPC over TLS sockets
- Challenge-response authentication
- TLS client handshake (certificate authentication)

As for HTTP Keep-Alive: It works, but I don't think it's very widely supported among client libraries and HTTP isn't really made for this type of thing, so my gut instinct would be to avoid it. That said, it doesn't hurt to offer the option.

On 3/3/2012 6:08 PM, Michael Grønager wrote:

HTTP and JSON-RPC are a client-server model; there is no way for the server to 
make calls to the client. It's not practical to expect clients to run their 
own JSON-RPC server - many cannot listen on WAN ports at all.

Well, I think what Stefan had in mind was http keep-alive combined with an event system. So similar to the way a web chat application work, just for json-rpc. BitcoinJS already uses this for realtime updating a webwallet. Libcoin is also prepared for this with a quite advanced, non-blocking, http server so I second Stefan that an update function could indeed be of relevance.

Btw - question to Stefan as the JavaScript guru - what do you consider the standard/defacto-standard/right/best-practice way of doing S->C json-rpc, what (javascript) library do you use for this?

Cheers,

Michael

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Virtualization & Cloud Management Using Capacity Planning
Cloud computing makes use of virtualization - but cloud computing 
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