Add "light client" support

[btiernay]

It would be great if one could subscribe to the network in a purely passive mode, without the need to sync. One use case is discussed here:

http://ethereum.stackexchange.com/questions/10125/is-it-possible-to-avoid-sync-in-ethereumj-but-still-register-a-listener

[Swaxxx]

Hello
I'm working on a project using your lib, and this feature is required by my client. I would like to know if this ticket is still active, or if there's another way to do that using EthereumJ.
Thank you

[mkalinin]

Hello @Swaxxx
The ticket is still relevant. And I hope this feature will be introduced in a close future

[adridadou]

Any plans or ETA for this?

[zilm13]

@adridadou we couldn't validate state root / receipts matching for incoming blocks if we don't have state, what do you propose? I have an idea to make something like light client for casper using EthereumJ, but no sense for that until Casper goes to Mainnet.

[adridadou]

I understand. I am interested in the feature but I haven't looked too deep into the details of it.
Maybe I'm missing something but shouldn't it be better to implement the LES protocol ?
https://github.com/ethereum/wiki/wiki/Light-client-protocol

This way you can use the network of servers that serve light clients and AFAIK the verification piece is solved there no?

[zilm13]

@adridadou looks cool!
As I see both Geth and Parity already support it. I didn't dive deeper to understand verification part but looks like it's solved. I couldn't provide any schedule or priority, but now we know that there is well established protocol for it.

[adridadou]

Glad I could help!
Yes the protocol seems pretty stable now and I think it will help us using a standard protocol instead of implementing our own.

I understand that you have no schedule but I hope this will help.
The geth and parity ppl are usually very helpful about that.

I think it make sense here also to split the task in two:

1. The LES client, i.e. the actual light client
2. The LES server, a full node to serve light clients