Suppose I have an HD public xpubkey and I derive bitcoin public address(es) from it.
Given one of the public bitcoin address derived from it e.g. 1F1tAaz5x1....
Can you get the xpubkey e.g. xpub6DKUi1BvKEgn...
I thought it is impossible, but someone I know claims it is possible.
And if it is possible isn't the privacy compromised in this situation?

Not sure if this is directly related but also take a look at
Deterministic Wallets, Their Advantages and their Understated Flaws ("An Understated Problem" section):
https://bitcoinmagazine.com/articles/deterministic-wallets-advantages-flaw-1385450276/

Thanks all.
Sorry, for wasting your time.  

Our sysadmin closed "some ports" this morning.
So it's all working fine now.
Thanks for the tips about "addnode"!

@Sellingaccs, Thanks.
I tried it. added the addresses you suggested.
The same results. "Connecting to peers..."

There is nothing I can re-install. All I'm using is the 64bit latest  binaries for Windows.
Everything worked fine yesterday and that's what makes me crazy.

Maybe my IP is banned somehow?

Im on the latest version 0.16.0.2
Both testnet and main. Its just stuck on "Connecting to peers..."

It was all fine yesterday. And my testnet was completely synced.
But now no peers at all.
No changes in my firewall.
I tried to delete the "peers.dat". Bitcoin ABC recreated it. but no peers again.

Is there any known peer list I could add?
How to resolve this?
 

Thanks

I am desperately needing Bitcoin Core 0.15.1 with addrindex binaries for Windows.
Is it anywhere available for download?

I have found this:
https://github.com/btcdrak/bitcoin/releases

But it only supports 0.13 which is way too old  

And I found this
https://github.com/unsystemizer/bitcoin-core-addrindex

But there are no binaries, and I'm not a c++ programmer.
I need  to reliably query transactions by external address that are not in the Bitcoin Core wallet(s) - to get balances for addresses.

I can query my 0.15.1 full node, for TXs by adding txindex=1 but the addrindex feature is missing (I wonder why such important feature is missing?)

I really don't want to use an old 0.13 version and don't want to depend on external API.

Please advice and I will be forever grateful.

Thanks guys! you gave me great tips, so I suppose the matter could be a bit more complex than I thought.
For now the privacy issue less concerns me (I know it's considered a "bad practice").
But I  noticed old and very small amounts txs (like 0.000001)  just hanging, so I thought I need to accumulate the small txs first.

Suppose I have 3 unspent outputs:

tx: 3 BTC
tx: 2 BTC
tx: 1 BTC

Now I want to spend 2.5 BTC.
Which is preferred as input(s) and why?

A single:
3 BTC (Leaving my an output change of 0.5)?

Or:
1 BTC + 2BTC? (Leaving my an output change of 0.5)

I hope the question is clear.

Thanks @goatpig for the useful information.  
I need to digest all of it, as I'm very new in the bitcoin world.
I never thought about the seed being tied to my server. I thought a backup command was available so I can copy/backup the wallets to a safe place.
Am I to understand that if I back up a wallet on machine A, and then restore it on machine B with Armory it could not be done? Again sorry for the dumb questions...

My model is quite simple as I already described. I want to be able to manage multiple wallets/account for our emploies on a headless server (I hope the terminology is correct).
This server will be protected and will have ports 8333 opened for the full node management i.e. bitcoind (and might also 8332 main/18332 tesntnet - for RPC internally).

The wallets files will be hold on the different server (or on the same server).

All the management will be done via a web-service (in our intranet only) talking to the bitcoind via RPC. e.g. opening new wallets; query of balance; send/receive funds; etc... I will be responsible for a web GUI talking to that web-service (talking to whatever full node via RPC).

What I was after is something like ethereum geth, which acts like a full-node, but lets me easily create and manage accounts (wallets) via RPC.

I toght Armory will let me do that bridge to the bitcoind, but the wallet managements will be done in Armory instead of bitcoind Wallets.

I installed python27 on Windows, then the Twisted package via:
pip install Twisted

All went well. copied the txjsonrpc folder to the Armory root folder.

Running python armoryd.py gives me an error:


What am I doing wrong?

Thanks!

 


I greatly appreciate your answer and your patience. As I already said, I'm quite sure I know what I'm doing and the risks involved. My objective is to create an internal intranet service  where we could manage different accounts (wallets) for employees.
Our server is well secured and I like to be able to manage wallets via an internal service that will "talk" to Armory via RPC (which will talk to bitcoind).
I love the fact that Armory is using bitcoind as a full node, but the downside of bitcoind is the lack of dynamic wallets management. Adding a new wallet requires shutting down the bitcoind, adding a wallet entry to the bitcoin.conf manually, and starting the bitcoind manually. this is quite annoying.

I find Armory to be very well designed, but I need the GUI functionality of managing wallets to be done via RPC including adding fresh new wallet for an employee instead of  doing that manually via GUI.
So I think this feature will be great for us and others!  

Thanks @droark!

Your comments were very helpful  

I went other the armoryd.py code, and the RPC conventions are very similar to bitcoind commands, which is great.
But no were I could find a method to create a new wallet file via RPC, and later on load it into the armoryd server list?

Found it!

adding set_lk_max_lockers (not set_lk_max_locks) did the trick:


https://docs.oracle.com/cd/E17276_01/html/api_reference/C/set_lk_max_lockers_parameter.html


I tested and was able to auto-create and load 932 wallets, until I hit an out of memory error in the db.log:


Which


Can resolve.

Using Process Monitor I verified that the DB_CONFIG is actually read by bitcoind.
If any one willing to try it out, here is the list of wallets you can drop into your bitcoin.conf: to reproduce

https://pastebin.com/8wHD1tL3

EDIT:

From the Berkeley DB  documentation: https://docs.oracle.com/cd/E17276_01/html/api_reference/C/set_lk_max_locks_parameter.html


What to make of this? is it impossible to change this parameter b/c the database environment already exists? or did I miss-read?

Sorry to have bothered you. I'm not familiar with Python at all, but that does not mean I don't know what I'm doing. I have used boitcoind RPC quit successfully, and it is build into their package ready to use.
You don't need to patronize. I know you are an Armory (main?) developer and probably know all the inside outs. but I am not, and willing to learn!

Replying that Armory can support creating a new wallet via Armory RPC with "Yes" is not helpful, if you can't say which command to use. I have looked into the armoryd.py source and did not find any code for command for that.
As I mentioned I got an error trying to run "python armoryd.py" (with Python 3.6 installed). I will install Python 2.7 and hopefully  that works for me.
Thanks again and keep doing a good job.  

Thanks for a clear answer. just to make it sure, if my wallet(s) are HD (which I do by default) I should not mind about keypool size and I can use 10 of 20 for that matter?

Also I made a mistake:


Should have been a fact, not a question.
When I tried to load/create 100 wallets (in multi-wallet mode), they were loaded/created in no time. as opposed when using the default 1000 keypool.

Does blockchain.info keeps my private key(s) in their wallets of database? I am referring to the wallets on their website.
What other private information do they use?

The default keypool is set to 1000. What does it mean exactly? That I have a pool of 1000 keys/address to use?
If I reduce the -keekpool to say 20 the wallet size is drastically reduced from 1.5M  to 50k. and loads much faster?
Will I be able to add more keys later? or after I finish the 20 pool I must re-use addresses? Is there any danger in a keypol of 20?

Any will help be appreciated.

Can you please explain a bit more? Aren't the full nodes belong to them?
It was also suggested that transactions might be not validated? How can a computer be connected to the block chain (node) without fully enforce all of the rules of Bitcoin and NOT using a full node?

I have already tried this. but the same results. As if this file is not read at all (?).

Can you please add a compiled armoryd.exe into the download package? That would be really great for us newbies!

BTW, can a new Armory wallet be created via RPC? if not, is there some other external way from outside ArmoryQt?