Example code fails, OpenError: IO error: ./.ethereum/state/LOCK: No such file or directory about ethereumjs-lib HOT 9 CLOSED

thanks for reporting! I'll look into it today First thing. 1) did you have cpp-ethereum running first? That guide just shows how to read cpp-ethereum's db. If you didn't run cpp-ethereum at some point there will be no DB. 2) Did you have cpp-ethereum running while you tried to read the DB? leveldb can't have more than one reader at a time. So you need to make use cpp-ethereum is not running while you are trying to read the DB.

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Thank you for the quick response! I opened and closed AlethZero, and I checked that ~/.ethereum/state/LOCK exists.

BTW, I noticed that the example code has .ethereum in the app's local directory. So I tried copying .ethereum to ./. LevelUp loaded the ./.ethereum/state database just fine, but when I changed

var db = levelup('./.ethereum/state');

to

var db = levelup('~/.ethereum/state');

so that .ethereum would be loaded from the home directory, I get the same error: "~/.ethereum/state/LOCK: No such file or directory", even though I checked, and the file does exist. I also tried running the code with root access, and nothing changed.

Edit: I found the problem. levelup doesn't process ~/ as my home directory. Using a relative path to the home directory fixes the problem. But I wonder why ~/ isn't processed as my home?

Now I'm just having the problem that I don't know how to copy a block's state's root from the AlethZero client.

BTW, I don't know where to post general usage questions, so I'll ask here: My goal currently is to have the Node server listen for transactions that go to a specific address and to trigger an event whenever a transaction arrives. I'm just starting looking at the API, and I'm wondering if this is possible yet.

from ethereumjs-lib.

I don't think "~" will work; you have to use the full path or a relative path.

... and I'm wondering if this is possible yet.

It is. But I probably need to update the docs. There are two ways to do it. Do you want to run a full node? ie actually validate and run VM. Or do you just want a 'dumb' node that listens to the network?

Here is how to do simple listener

var Network = require('ethereumjs-lib').Network;
var network = new Network({
  ethVersion: 32, 
  capabilities: ['eth']
});

//the protocol requires that we send a genesis hash after we connect so that we 
// know we have the correct blockchain. Currently the genesis the following
var genesisHash = new Buffer('08436a4d33c77e6acf013e586a3333ad152f25d31df8b68749d85046810e1f4b', 'hex');

//send our status.
network.on('message.hello', function (hello, peer) {
    //arguments: totally difficultly, highest block, genesisHash
  peer.sendStatus(new Buffer([0]), genesisHash, genesisHash);
  console.log('networking', 'hello from: ' + hello.clientId + ' version:' + hello.protocolVersion);
});

network.on('message.transactions', function (txs) {
  txs.forEach(function(tx){
    //you can insert your logic here. 
    console.log('got a transaction to: ' + tx.to.toString('hex'));
  });
});

network.listen(30303, "0.0.0.0");
//or use network.connect

Lastly feel free to open new issue if you have more questions like this.

from ethereumjs-lib.

Thanks!

That code looks easy enough to use. Unfortunately, when I run it, I never get a hello message, so nothing happens. Any idea what's gone wrong? I'm confused about the code -- the "//arguments: totally difficultly, highest block, genesisHash" comment doesn't seem to match any code.

For now, I'll stick to a 'dumb' node, but I'd like to try a full node in the future. I'm just experimenting with Ethereum right now to see what I can do. My first project is to prove to the server that the client owns an Ethereum address.

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when I run it, I never get a hello message

Right, that's because its only listening. If you have another client such cpp-ethereum you can connect to it. Or you can initiate a connection with network.listen(port, ip);

As far as the send status that is pretty new and it is not in the docs yet. If you want to read about the protocol see here

from ethereumjs-lib.

OK. I changed it to "network.connect(30303, "poc-6.ethdev.com");"

It connects and gets a hello message, but it disconnects immediately after, so it never gets any blocks or messages. :(

I also tried using "network.listen(30304, "0.0.0.0");" and connecting to it with the AlethZero client. Same thing. I get a hello message and then immediately disconnect.

from ethereumjs-lib.

I'm going to try this out. But off the top of my head I'm guesing network version is wrong. I tested the above snippet against version 32. I think we are now at 33. I'll try to get you an update ASAP.

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Hi Martin,

Changing the version number to 33 didn't work. Still haven't gotten the library to successfully connect to ethereum.

I'm going to close this issue though and open up a new one.

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@ldurback I added PoC7 networking and this is working for me now

var Network = require('ethereumjs-lib').Network;
var network = new Network();

var genesisHash = new Buffer('08436a4d33c77e6acf013e586a3333ad152f25d31df8b68749d85046810e1f4b', 'hex');

network.on('message.hello', function (hello, peer) {
  peer.sendStatus(new Buffer([0]), genesisHash, genesisHash);
  console.log('networking', 'hello from: ' + hello.clientId + ' version:' + hello.protocolVersion);
});

network.on('message.transactions', function (txs) {
  txs.forEach(function (tx) {
    console.log('got a transaction to: ' + tx.to.toString('hex'));
  });
});

network.on('message.disconnect', function (dis) {
  console.log('networking', 'dissconect: ' + dis.reason);
});


network.listen(30303, "0.0.0.0");
network.connect(30303, "poc-7.ethdev.com");

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